From 96697f11dbba4d0a61fce465d40858649b0096c3 Mon Sep 17 00:00:00 2001
From: echedey-ls <80125792+echedey-ls@users.noreply.github.com>
Date: Wed, 8 Jan 2025 21:41:21 +0000
Subject: [PATCH 01/15] Add cross_axis_tilt to nomenclature.rst

Definition via https://pvlib-python.readthedocs.io/en/stable/reference/generated/pvlib.tracking.calc_cross_axis_tilt.html
---
 docs/sphinx/source/user_guide/nomenclature.rst | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/docs/sphinx/source/user_guide/nomenclature.rst b/docs/sphinx/source/user_guide/nomenclature.rst
index f361690f73..61285211e8 100644
--- a/docs/sphinx/source/user_guide/nomenclature.rst
+++ b/docs/sphinx/source/user_guide/nomenclature.rst
@@ -36,6 +36,18 @@ There is a convention on consistent variable names throughout the library:
     bhi
         Beam/direct horizontal irradiance
 
+    cross_axis_tilt
+        Cross-axis tilt angle [°].
+        Consider two parallel rows of modules at different height;
+        ``cross_axis_tilt`` is the angle formed by the line formed by the
+        intersection between the slope containing the tracker axes and a plane
+        perpendicular to the tracker axes, and the horizontal plane.
+        Cross-axis tilt is measured by using a right-handed convention.
+        For example, trackers with axis azimuth of 180 degrees (heading south)
+        will have a negative cross-axis tilt if the tracker axes plane slopes
+        down to the east and positive cross-axis tilt if the tracker axes plane
+        slopes up to the east.
+
     dhi
         Diffuse horizontal irradiance
 

From 8eebd5faab3c68992fb29ef9a3e7d74227b23889 Mon Sep 17 00:00:00 2001
From: echedey-ls <80125792+echedey-ls@users.noreply.github.com>
Date: Wed, 8 Jan 2025 21:43:44 +0000
Subject: [PATCH 02/15] Rename, cross_axis_slope -> cross_axis_tilt

---
 .../shading/plot_martinez_shade_loss.py       |  2 +-
 .../plot_shaded_fraction1d_ns_hsat_example.py | 12 +++++------
 pvlib/shading.py                              | 20 +++++++++----------
 pvlib/tests/test_shading.py                   |  4 ++--
 4 files changed, 19 insertions(+), 19 deletions(-)

diff --git a/docs/examples/shading/plot_martinez_shade_loss.py b/docs/examples/shading/plot_martinez_shade_loss.py
index 10ce77f741..b30b6e4c12 100644
--- a/docs/examples/shading/plot_martinez_shade_loss.py
+++ b/docs/examples/shading/plot_martinez_shade_loss.py
@@ -116,7 +116,7 @@
     shading_row_rotation=tracker_theta,
     collector_width=width,
     pitch=pitch,
-    cross_axis_slope=cross_axis_tilt,
+    cross_axis_tilt=cross_axis_tilt,
 )
 
 # %%
diff --git a/docs/examples/shading/plot_shaded_fraction1d_ns_hsat_example.py b/docs/examples/shading/plot_shaded_fraction1d_ns_hsat_example.py
index 7eae2ed7aa..9a1e942e5d 100644
--- a/docs/examples/shading/plot_shaded_fraction1d_ns_hsat_example.py
+++ b/docs/examples/shading/plot_shaded_fraction1d_ns_hsat_example.py
@@ -49,7 +49,7 @@
 collector_width = 3.2  # m
 pitch = 4.15  # m
 gcr = collector_width / pitch
-cross_axis_slope = -5  # degrees
+cross_axis_tilt = -5  # degrees
 surface_to_axis_offset = 0.07  # m
 
 # Generate a time range for the simulation
@@ -76,7 +76,7 @@
     max_angle=(-50, 50),  # (min, max) degrees
     backtrack=False,
     gcr=gcr,
-    cross_axis_tilt=cross_axis_slope,
+    cross_axis_tilt=cross_axis_tilt,
 )["tracker_theta"]
 
 # %%
@@ -112,7 +112,7 @@
         collector_width=collector_width,
         pitch=pitch,
         surface_to_axis_offset=surface_to_axis_offset,
-        cross_axis_slope=cross_axis_slope,
+        cross_axis_tilt=cross_axis_tilt,
         shading_row_rotation=rotation_angle,
     ),
 )
@@ -130,7 +130,7 @@
         collector_width=collector_width,
         pitch=pitch,
         surface_to_axis_offset=surface_to_axis_offset,
-        cross_axis_slope=cross_axis_slope,
+        cross_axis_tilt=cross_axis_tilt,
         shading_row_rotation=rotation_angle,
     ),
     # shaded fraction in the evening
@@ -143,7 +143,7 @@
         collector_width=collector_width,
         pitch=pitch,
         surface_to_axis_offset=surface_to_axis_offset,
-        cross_axis_slope=cross_axis_slope,
+        cross_axis_tilt=cross_axis_tilt,
         shading_row_rotation=rotation_angle,
     ),
 )
@@ -161,7 +161,7 @@
         collector_width=collector_width,
         pitch=pitch,
         surface_to_axis_offset=surface_to_axis_offset,
-        cross_axis_slope=cross_axis_slope,
+        cross_axis_tilt=cross_axis_tilt,
         shading_row_rotation=rotation_angle,
     ),
     0,  # no shaded fraction in the evening
diff --git a/pvlib/shading.py b/pvlib/shading.py
index 42aef892f7..0bdd40dbfb 100644
--- a/pvlib/shading.py
+++ b/pvlib/shading.py
@@ -354,7 +354,7 @@ def shaded_fraction1d(
     pitch,
     axis_tilt=0,
     surface_to_axis_offset=0,
-    cross_axis_slope=0,
+    cross_axis_tilt=0,
     shading_row_rotation=None,
 ):
     r"""
@@ -397,7 +397,7 @@ def shaded_fraction1d(
     surface_to_axis_offset : numeric, default 0
         Distance between the rotating axis and the collector surface.
         May be used to account for a torque tube offset.
-    cross_axis_slope : numeric, default 0
+    cross_axis_tilt : numeric, default 0
         Angle of the plane containing the rows' axes from
         horizontal. Right-handed rotation with respect to the rows axes.
         In degrees :math:`^{\circ}`.
@@ -430,7 +430,7 @@ def shaded_fraction1d(
     +------------------+----------------------------+                     |
     | :math:`\theta_2` | ``shaded_row_rotation``    | Degrees             |
     +------------------+----------------------------+ :math:`^{\circ}`    |
-    | :math:`\beta_c`  | ``cross_axis_slope``       |                     |
+    | :math:`\beta_c`  | ``cross_axis_tilt``        |                     |
     +------------------+----------------------------+---------------------+
     | :math:`p`        | ``pitch``                  | Any consistent      |
     +------------------+----------------------------+ length unit across  |
@@ -452,7 +452,7 @@ def shaded_fraction1d(
     >>> shaded_fraction1d(solar_zenith=80, solar_azimuth=135,
     ...     axis_azimuth=90, shaded_row_rotation=30, shading_row_rotation=30,
     ...     collector_width=2, pitch=3, axis_tilt=0,
-    ...     surface_to_axis_offset=0.05, cross_axis_slope=0)
+    ...     surface_to_axis_offset=0.05, cross_axis_tilt=0)
     0.47755694708090535
 
     **Fixed-tilt north-facing array on sloped terrain**
@@ -466,7 +466,7 @@ def shaded_fraction1d(
     >>> shaded_fraction1d(solar_zenith=80, solar_azimuth=75.5,
     ...     axis_azimuth=270, shaded_row_rotation=50, shading_row_rotation=30,
     ...     collector_width=2.5, pitch=4, axis_tilt=10,
-    ...     surface_to_axis_offset=0.05, cross_axis_slope=0)
+    ...     surface_to_axis_offset=0.05, cross_axis_tilt=0)
     0.793244836197256
 
     **N-S single-axis tracker on sloped terrain**
@@ -478,7 +478,7 @@ def shaded_fraction1d(
 
     >>> shaded_fraction1d(solar_zenith=80, solar_azimuth=90, axis_azimuth=180,
     ...     shaded_row_rotation=-30, collector_width=1.4, pitch=3, axis_tilt=0,
-    ...     surface_to_axis_offset=0.10, cross_axis_slope=7)
+    ...     surface_to_axis_offset=0.10, cross_axis_tilt=7)
     0.8242176864434579
 
     Note the previous example only is valid for the shaded fraction of the
@@ -493,7 +493,7 @@ def shaded_fraction1d(
 
     >>> shaded_fraction1d(solar_zenith=80, solar_azimuth=270, axis_azimuth=180,
     ...     shaded_row_rotation=30, collector_width=1.4, pitch=3, axis_tilt=0,
-    ...     surface_to_axis_offset=0.10, cross_axis_slope=7)
+    ...     surface_to_axis_offset=0.10, cross_axis_tilt=7)
     0.018002567182254348
 
     You must switch the input/output depending on the
@@ -528,7 +528,7 @@ def shaded_fraction1d(
     # calculate repeated elements
     thetas_1_S_diff = shading_row_rotation - projected_solar_zenith
     thetas_2_S_diff = shaded_row_rotation - projected_solar_zenith
-    thetaS_rotation_diff = projected_solar_zenith - cross_axis_slope
+    thetaS_rotation_diff = projected_solar_zenith - cross_axis_tilt
 
     cos_theta_2_S_diff_abs = np.abs(cosd(thetas_2_S_diff))
 
@@ -548,7 +548,7 @@ def shaded_fraction1d(
             / collector_width
             * cosd(thetaS_rotation_diff)
             / cos_theta_2_S_diff_abs
-            / cosd(cross_axis_slope)
+            / cosd(cross_axis_tilt)
         )
     )
 
@@ -660,7 +660,7 @@ def direct_martinez(
     >>>     solar_zenith=80, solar_azimuth=180,
     >>>     axis_azimuth=90, shaded_row_rotation=25,
     >>>     collector_width=0.5, pitch=1, surface_to_axis_offset=0,
-    >>>     cross_axis_slope=5.711, shading_row_rotation=50)
+    >>>     cross_axis_tilt=5.711, shading_row_rotation=50)
     >>> # calculation of the number of shaded blocks
     >>> shaded_blocks = np.ceil(total_blocks*shaded_fraction)
     >>> # apply the Martinez power losses to the calculated shading
diff --git a/pvlib/tests/test_shading.py b/pvlib/tests/test_shading.py
index f83f2db47b..3887dd8fd9 100644
--- a/pvlib/tests/test_shading.py
+++ b/pvlib/tests/test_shading.py
@@ -258,7 +258,7 @@ def sf1d_premises_and_expected():
         ),
     )  # fmt: skip
 
-    test_data["cross_axis_slope"] = atand(
+    test_data["cross_axis_tilt"] = atand(
         (test_data["z_R"] - test_data["z_L"])
         / (test_data["x_L"] - test_data["x_R"])
     )
@@ -314,7 +314,7 @@ def test_shaded_fraction1d_unprovided_shading_row_rotation():
     test_data = pd.DataFrame(
         columns=[
             "shaded_row_rotation", "surface_to_axis_offset", "collector_width",
-            "solar_zenith", "cross_axis_slope", "pitch", "solar_azimuth",
+            "solar_zenith", "cross_axis_tilt", "pitch", "solar_azimuth",
             "axis_azimuth", "expected_sf",
         ],
         data=[

From 0aa883697bab97a7e85c5e0849d1f195a93070dc Mon Sep 17 00:00:00 2001
From: echedey-ls <80125792+echedey-ls@users.noreply.github.com>
Date: Wed, 8 Jan 2025 21:53:10 +0000
Subject: [PATCH 03/15] Add renamed_kwarg_warning

---
 pvlib/shading.py            |  8 ++++++++
 pvlib/tests/test_shading.py | 19 +++++++++++++++++++
 2 files changed, 27 insertions(+)

diff --git a/pvlib/shading.py b/pvlib/shading.py
index 0bdd40dbfb..b3e9f8822e 100644
--- a/pvlib/shading.py
+++ b/pvlib/shading.py
@@ -7,6 +7,8 @@
 import pandas as pd
 from pvlib.tools import sind, cosd
 
+from pvlib._deprecation import renamed_kwarg_warning
+
 
 def ground_angle(surface_tilt, gcr, slant_height):
     """
@@ -344,6 +346,12 @@ def projected_solar_zenith_angle(solar_zenith, solar_azimuth,
     return theta_T
 
 
+@renamed_kwarg_warning(
+    since="0.11.3",
+    old_param_name="cross_axis_slope",
+    new_param_name="cross_axis_tilt",
+    removal="0.13.0",
+)
 def shaded_fraction1d(
     solar_zenith,
     solar_azimuth,
diff --git a/pvlib/tests/test_shading.py b/pvlib/tests/test_shading.py
index 3887dd8fd9..8a0529222b 100644
--- a/pvlib/tests/test_shading.py
+++ b/pvlib/tests/test_shading.py
@@ -9,6 +9,9 @@
 from pvlib import shading
 from pvlib.tools import atand
 
+from pvlib.tests.conftest import fail_on_pvlib_version
+from pvlib._deprecation import pvlibDeprecationWarning
+
 
 @pytest.fixture
 def test_system():
@@ -329,6 +332,22 @@ def test_shaded_fraction1d_unprovided_shading_row_rotation():
     assert_allclose(sf, expected_sf, atol=1e-2)
 
 
+@fail_on_pvlib_version("0.13.0")
+def test_shaded_fraction1d_renamed_cross_axis_slope2cross_axis_tilt():
+    # Tests shaded_fraction1d with cross_axis_slope instead of cross_axis_tilt
+    with pytest.warns(pvlibDeprecationWarning, match="cross_axis_slope"):
+        shading.shaded_fraction1d(
+            solar_zenith=60,
+            solar_azimuth=90,
+            axis_azimuth=180,
+            shaded_row_rotation=30,
+            collector_width=3,
+            pitch=7,
+            surface_to_axis_offset=0,
+            cross_axis_slope=0,
+        )
+
+
 @pytest.fixture
 def direct_martinez_Table2():
     """

From 01d5c0b11be881bfec44277304eb386b1d6391d3 Mon Sep 17 00:00:00 2001
From: echedey-ls <80125792+echedey-ls@users.noreply.github.com>
Date: Wed, 8 Jan 2025 21:57:31 +0000
Subject: [PATCH 04/15] Fix typo in renamed_kwarg_warning docstring

---
 pvlib/_deprecation.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/pvlib/_deprecation.py b/pvlib/_deprecation.py
index aedb4d5096..06d35959e0 100644
--- a/pvlib/_deprecation.py
+++ b/pvlib/_deprecation.py
@@ -334,7 +334,7 @@ def renamed_kwarg_warning(since, old_param_name, new_param_name, removal=""):
         Not compatible with positional-only arguments.
 
     .. note::
-        Documentation for the function may updated to reflect the new parameter
+        Affected function docstring may be updated to reflect the new parameter
         name; it is suggested to add a |.. versionchanged::| directive.
 
     Parameters

From e72ca3215b0cc98ac20403d5028ebbabe667a2cf Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Echedey=20Luis=20=C3=81lvarez?=
 <80125792+echedey-ls@users.noreply.github.com>
Date: Sun, 7 Sep 2025 20:20:47 +0100
Subject: [PATCH 05/15] Deprecate in v0.13.1 / Removal in v0.15.0

---
 pvlib/shading.py            | 4 ++--
 pvlib/tests/test_shading.py | 2 +-
 2 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/pvlib/shading.py b/pvlib/shading.py
index b3e9f8822e..fa5f534701 100644
--- a/pvlib/shading.py
+++ b/pvlib/shading.py
@@ -347,10 +347,10 @@ def projected_solar_zenith_angle(solar_zenith, solar_azimuth,
 
 
 @renamed_kwarg_warning(
-    since="0.11.3",
+    since="0.13.1",
     old_param_name="cross_axis_slope",
     new_param_name="cross_axis_tilt",
-    removal="0.13.0",
+    removal="0.15.0",
 )
 def shaded_fraction1d(
     solar_zenith,
diff --git a/pvlib/tests/test_shading.py b/pvlib/tests/test_shading.py
index 8a0529222b..986cab3054 100644
--- a/pvlib/tests/test_shading.py
+++ b/pvlib/tests/test_shading.py
@@ -332,7 +332,7 @@ def test_shaded_fraction1d_unprovided_shading_row_rotation():
     assert_allclose(sf, expected_sf, atol=1e-2)
 
 
-@fail_on_pvlib_version("0.13.0")
+@fail_on_pvlib_version("0.15.0")
 def test_shaded_fraction1d_renamed_cross_axis_slope2cross_axis_tilt():
     # Tests shaded_fraction1d with cross_axis_slope instead of cross_axis_tilt
     with pytest.warns(pvlibDeprecationWarning, match="cross_axis_slope"):

From 08bcde47a31521e1d9487f7f6d7f619a961e27ef Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Echedey=20Luis=20=C3=81lvarez?=
 <80125792+echedey-ls@users.noreply.github.com>
Date: Sun, 7 Sep 2025 20:47:46 +0100
Subject: [PATCH 06/15] move descriptions, link to nomenclature term

---
 docs/sphinx/source/user_guide/nomenclature.rst |  2 ++
 pvlib/shading.py                               |  4 ++--
 pvlib/tracking.py                              | 14 ++++----------
 3 files changed, 8 insertions(+), 12 deletions(-)

diff --git a/docs/sphinx/source/user_guide/nomenclature.rst b/docs/sphinx/source/user_guide/nomenclature.rst
index 61285211e8..827fb99edb 100644
--- a/docs/sphinx/source/user_guide/nomenclature.rst
+++ b/docs/sphinx/source/user_guide/nomenclature.rst
@@ -47,6 +47,8 @@ There is a convention on consistent variable names throughout the library:
         will have a negative cross-axis tilt if the tracker axes plane slopes
         down to the east and positive cross-axis tilt if the tracker axes plane
         slopes up to the east.
+        Use :func:`~pvlib.tracking.calc_cross_axis_tilt` to calculate
+        ``cross_axis_tilt``
 
     dhi
         Diffuse horizontal irradiance
diff --git a/pvlib/shading.py b/pvlib/shading.py
index fa5f534701..7be2b62ca5 100644
--- a/pvlib/shading.py
+++ b/pvlib/shading.py
@@ -406,9 +406,9 @@ def shaded_fraction1d(
         Distance between the rotating axis and the collector surface.
         May be used to account for a torque tube offset.
     cross_axis_tilt : numeric, default 0
-        Angle of the plane containing the rows' axes from
+        Angle of the plane containing the rows' axes relative to
         horizontal. Right-handed rotation with respect to the rows axes.
-        In degrees :math:`^{\circ}`.
+        See :term:`cross_axis_tilt`. In degrees :math:`^{\circ}`.
     shading_row_rotation : numeric, optional
         Right-handed rotation of the row casting the shadow, with respect
         to the row axis. In degrees :math:`^{\circ}`.
diff --git a/pvlib/tracking.py b/pvlib/tracking.py
index afdaab2adf..3e04e7cc5f 100644
--- a/pvlib/tracking.py
+++ b/pvlib/tracking.py
@@ -9,7 +9,7 @@
 def singleaxis(apparent_zenith, apparent_azimuth,
                axis_tilt=0, axis_azimuth=0, max_angle=90,
                backtrack=True, gcr=2.0/7.0, cross_axis_tilt=0):
-    """
+    r"""
     Determine the rotation angle of a single-axis tracker when given particular
     solar zenith and azimuth angles.
 
@@ -75,15 +75,9 @@ def singleaxis(apparent_zenith, apparent_azimuth,
         2/7 is default. ``gcr`` must be <=1.
 
     cross_axis_tilt : float, default 0.0
-        The angle, relative to horizontal, of the line formed by the
-        intersection between the slope containing the tracker axes and a plane
-        perpendicular to the tracker axes. The cross-axis tilt should be
-        specified using a right-handed convention. For example, trackers with
-        axis azimuth of 180 degrees (heading south) will have a negative
-        cross-axis tilt if the tracker axes plane slopes down to the east and
-        positive cross-axis tilt if the tracker axes plane slopes down to the
-        west. Use :func:`~pvlib.tracking.calc_cross_axis_tilt` to calculate
-        ``cross_axis_tilt``. [degrees]
+        Angle of the plane containing the rows' axes relative to
+        horizontal. Right-handed rotation with respect to the rows axes.
+        See :term:`cross_axis_tilt`. In degrees :math:`^{\circ}`.
 
     Returns
     -------

From 3ca225e7352bdeaf22f26b8b9e7ba659a0b32de9 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Echedey=20Luis=20=C3=81lvarez?=
 <80125792+echedey-ls@users.noreply.github.com>
Date: Sun, 7 Sep 2025 20:57:35 +0100
Subject: [PATCH 07/15] merge fix

---
 tests/test_shading.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tests/test_shading.py b/tests/test_shading.py
index 986cab3054..a19917774b 100644
--- a/tests/test_shading.py
+++ b/tests/test_shading.py
@@ -9,7 +9,7 @@
 from pvlib import shading
 from pvlib.tools import atand
 
-from pvlib.tests.conftest import fail_on_pvlib_version
+from .conftest import fail_on_pvlib_version
 from pvlib._deprecation import pvlibDeprecationWarning
 
 

From c74127c4138233cb5e7e6cddf7253387aa5f2101 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Echedey=20Luis=20=C3=81lvarez?=
 <80125792+echedey-ls@users.noreply.github.com>
Date: Sun, 7 Sep 2025 20:57:42 +0100
Subject: [PATCH 08/15] whatsnew

---
 docs/sphinx/source/whatsnew/v0.13.1.rst | 1 +
 1 file changed, 1 insertion(+)

diff --git a/docs/sphinx/source/whatsnew/v0.13.1.rst b/docs/sphinx/source/whatsnew/v0.13.1.rst
index 26a591e534..58bf5664a4 100644
--- a/docs/sphinx/source/whatsnew/v0.13.1.rst
+++ b/docs/sphinx/source/whatsnew/v0.13.1.rst
@@ -13,6 +13,7 @@ Deprecations
 * Deprecate :py:func:`~pvlib.modelchain.get_orientation`. (:pull:`2495`)
 * Rename parameter name ``aparent_azimuth`` to ``solar_azimuth`` in :py:func:`~pvlib.tracking.singleaxis`.
   (:issue:`2479`, :pull:`2480`)
+* Rename parameter ``cross_axis_slope`` to ``cross_axis_tilt`` in :py:func:`pvlib.shading.shaded_fraction1d`. (:issue:`2334`, :pull:`2543`)
 
 Bug fixes
 ~~~~~~~~~

From 3006aa15acefb7726099effed42e76466458a553 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Echedey=20Luis=20=C3=81lvarez?=
 <80125792+echedey-ls@users.noreply.github.com>
Date: Sat, 20 Sep 2025 22:07:50 +0200
Subject: [PATCH 09/15] Dax review

Co-Authored-By: RDaxini <143435106+RDaxini@users.noreply.github.com>
---
 docs/sphinx/source/user_guide/extras/nomenclature.rst | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/docs/sphinx/source/user_guide/extras/nomenclature.rst b/docs/sphinx/source/user_guide/extras/nomenclature.rst
index e5bf41091c..6c6ad92514 100644
--- a/docs/sphinx/source/user_guide/extras/nomenclature.rst
+++ b/docs/sphinx/source/user_guide/extras/nomenclature.rst
@@ -45,13 +45,13 @@ There is a convention on consistent variable names throughout the library:
         Beam/direct horizontal irradiance
 
     cross_axis_tilt
-        Cross-axis tilt angle [°].
+        Cross-axis tilt angle. [°]
         Consider two parallel rows of modules at different height;
-        ``cross_axis_tilt`` is the angle formed by the line formed by the
+        ``cross_axis_tilt`` is the angle formed the line formed by the
         intersection between the slope containing the tracker axes and a plane
         perpendicular to the tracker axes, and the horizontal plane.
         Cross-axis tilt is measured by using a right-handed convention.
-        For example, trackers with axis azimuth of 180 degrees (heading south)
+        For example, trackers with axis azimuth of 180° (heading south)
         will have a negative cross-axis tilt if the tracker axes plane slopes
         down to the east and positive cross-axis tilt if the tracker axes plane
         slopes up to the east.

From 2cebae7d71cef29a87096e158c8f8103cc52f800 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Echedey=20Luis=20=C3=81lvarez?=
 <80125792+echedey-ls@users.noreply.github.com>
Date: Wed, 24 Sep 2025 11:41:40 +0200
Subject: [PATCH 10/15] Change: deprecate *axis_tilt in favour of *axis_slope

---
 benchmarks/benchmarks/infinite_sheds.py       |   2 +-
 benchmarks/benchmarks/tracking.py             |   2 +-
 docs/examples/bifacial/plot_bifi_model_mc.py  |   4 +-
 .../plot_transposition_gain.py                |   2 +-
 .../shading/plot_martinez_shade_loss.py       |  14 +-
 .../plot_shaded_fraction1d_ns_hsat_example.py |  26 ++--
 .../plot_discontinuous_tracking.py            |   6 +-
 .../plot_single_axis_tracking.py              |   4 +-
 ..._single_axis_tracking_on_sloped_terrain.py |  28 ++--
 docs/sphinx/source/reference/tracking.rst     |   4 +-
 .../source/user_guide/extras/nomenclature.rst |   8 +-
 docs/sphinx/source/whatsnew/v0.13.1.rst       |  12 +-
 docs/sphinx/source/whatsnew/v0.8.0.rst        |   6 +-
 pvlib/modelchain.py                           |   2 +-
 pvlib/pvsystem.py                             |  93 +++++++++++--
 pvlib/shading.py                              |  83 +++++++-----
 pvlib/tracking.py                             | 121 ++++++++++++-----
 tests/test_pvsystem.py                        |  42 +++++-
 tests/test_shading.py                         |  50 ++++---
 tests/test_tracking.py                        | 127 ++++++++++++------
 20 files changed, 441 insertions(+), 195 deletions(-)

diff --git a/benchmarks/benchmarks/infinite_sheds.py b/benchmarks/benchmarks/infinite_sheds.py
index 755c2ec3ef..d5a3de1033 100644
--- a/benchmarks/benchmarks/infinite_sheds.py
+++ b/benchmarks/benchmarks/infinite_sheds.py
@@ -35,7 +35,7 @@ def setup(self, vectorize):
             self.tracking = tracking.singleaxis(
                 self.solar_position['apparent_zenith'],
                 self.solar_position['azimuth'],
-                axis_tilt=0,
+                axis_slope=0,
                 axis_azimuth=0,
                 max_angle=60,
                 backtrack=True,
diff --git a/benchmarks/benchmarks/tracking.py b/benchmarks/benchmarks/tracking.py
index 29f5ac4c6e..0308a65d38 100644
--- a/benchmarks/benchmarks/tracking.py
+++ b/benchmarks/benchmarks/tracking.py
@@ -22,7 +22,7 @@ def time_singleaxis(self):
         with np.errstate(invalid='ignore'):
             tracking.singleaxis(self.solar_position.apparent_zenith,
                                 self.solar_position.azimuth,
-                                axis_tilt=0,
+                                axis_slope=0,
                                 axis_azimuth=0,
                                 max_angle=60,
                                 backtrack=True,
diff --git a/docs/examples/bifacial/plot_bifi_model_mc.py b/docs/examples/bifacial/plot_bifi_model_mc.py
index 679ff22921..61e801277d 100644
--- a/docs/examples/bifacial/plot_bifi_model_mc.py
+++ b/docs/examples/bifacial/plot_bifi_model_mc.py
@@ -43,7 +43,7 @@
 times = pd.date_range('2021-06-21', '2021-6-22', freq='1T', tz=tz)
 
 # create site system characteristics
-axis_tilt = 0
+axis_slope = 0
 axis_azimuth = 180
 gcr = 0.35
 max_angle = 60
@@ -65,7 +65,7 @@
 cs = site_location.get_clearsky(times)
 
 # load solar position and tracker orientation for use in pvsystem object
-sat_mount = pvsystem.SingleAxisTrackerMount(axis_tilt=axis_tilt,
+sat_mount = pvsystem.SingleAxisTrackerMount(axis_slope=axis_slope,
                                             axis_azimuth=axis_azimuth,
                                             max_angle=max_angle,
                                             backtrack=True,
diff --git a/docs/examples/irradiance-transposition/plot_transposition_gain.py b/docs/examples/irradiance-transposition/plot_transposition_gain.py
index e0b7031f0b..02fe7e634a 100644
--- a/docs/examples/irradiance-transposition/plot_transposition_gain.py
+++ b/docs/examples/irradiance-transposition/plot_transposition_gain.py
@@ -85,7 +85,7 @@ def calculate_poa(tmy, solar_position, surface_tilt, surface_azimuth):
 # single-axis tracking:
 orientation = tracking.singleaxis(solar_position['apparent_zenith'],
                                   solar_position['azimuth'],
-                                  axis_tilt=0,  # flat array
+                                  axis_slope=0,  # flat array
                                   axis_azimuth=180,  # south-facing azimuth
                                   max_angle=60,  # a common maximum rotation
                                   backtrack=True,  # backtrack for a c-Si array
diff --git a/docs/examples/shading/plot_martinez_shade_loss.py b/docs/examples/shading/plot_martinez_shade_loss.py
index 6423017567..d8f0d7e0f3 100644
--- a/docs/examples/shading/plot_martinez_shade_loss.py
+++ b/docs/examples/shading/plot_martinez_shade_loss.py
@@ -54,8 +54,8 @@
 gcr = width / pitch  # ground coverage ratio
 N_modules_per_row = 6
 axis_azimuth = 180  # N-S axis
-axis_tilt = 0  # flat because the axis is perpendicular to the slope
-cross_axis_tilt = -7  # 7 degrees downward to the east
+axis_slope = 0  # flat because the axis is perpendicular to the slope
+cross_axis_slope = -7  # 7 degrees downward to the east
 
 latitude, longitude = 40.2712, -3.7277
 locus = pvlib.location.Location(
@@ -91,12 +91,12 @@
 tracking_result = pvlib.tracking.singleaxis(
     apparent_zenith=solar_apparent_zenith,
     solar_azimuth=solar_azimuth,
-    axis_tilt=axis_tilt,
+    axis_slope=axis_slope,
     axis_azimuth=axis_azimuth,
-    max_angle=(-90 + cross_axis_tilt, 90 + cross_axis_tilt),  # (min, max)
+    max_angle=(-90 + cross_axis_slope, 90 + cross_axis_slope),  # (min, max)
     backtrack=False,
     gcr=gcr,
-    cross_axis_tilt=cross_axis_tilt,
+    cross_axis_slope=cross_axis_slope,
 )
 
 tracker_theta, aoi, surface_tilt, surface_azimuth = (
@@ -111,12 +111,12 @@
     solar_apparent_zenith,
     solar_azimuth,
     axis_azimuth,
-    axis_tilt=axis_tilt,
+    axis_slope=axis_slope,
     shaded_row_rotation=tracker_theta,
     shading_row_rotation=tracker_theta,
     collector_width=width,
     pitch=pitch,
-    cross_axis_tilt=cross_axis_tilt,
+    cross_axis_slope=cross_axis_slope,
 )
 
 # %%
diff --git a/docs/examples/shading/plot_shaded_fraction1d_ns_hsat_example.py b/docs/examples/shading/plot_shaded_fraction1d_ns_hsat_example.py
index 9a1e942e5d..f216732f5d 100644
--- a/docs/examples/shading/plot_shaded_fraction1d_ns_hsat_example.py
+++ b/docs/examples/shading/plot_shaded_fraction1d_ns_hsat_example.py
@@ -44,12 +44,12 @@
 latitude, longitude = 28.51, -13.89
 altitude = pvlib.location.lookup_altitude(latitude, longitude)
 
-axis_tilt = 3  # degrees, positive is upwards in the axis_azimuth direction
+axis_slope = 3  # degrees, positive is upwards in the axis_azimuth direction
 axis_azimuth = 180  # degrees, N-S tracking axis
 collector_width = 3.2  # m
 pitch = 4.15  # m
 gcr = collector_width / pitch
-cross_axis_tilt = -5  # degrees
+cross_axis_slope = -5  # degrees
 surface_to_axis_offset = 0.07  # m
 
 # Generate a time range for the simulation
@@ -71,12 +71,12 @@
 rotation_angle = pvlib.tracking.singleaxis(
     solar_zenith,
     solar_azimuth,
-    axis_tilt,
+    axis_slope,
     axis_azimuth,
     max_angle=(-50, 50),  # (min, max) degrees
     backtrack=False,
     gcr=gcr,
-    cross_axis_tilt=cross_axis_tilt,
+    cross_axis_slope=cross_axis_slope,
 )["tracker_theta"]
 
 # %%
@@ -95,7 +95,7 @@
 # failure or with a different system configuration.
 
 psza = pvlib.shading.projected_solar_zenith_angle(
-    solar_zenith, solar_azimuth, axis_tilt, axis_azimuth
+    solar_zenith, solar_azimuth, axis_slope, axis_azimuth
 )
 
 # Calculate the shaded fraction for the eastmost row
@@ -108,11 +108,11 @@
         solar_azimuth,
         axis_azimuth,
         shaded_row_rotation=rotation_angle,
-        axis_tilt=axis_tilt,
+        axis_slope=axis_slope,
         collector_width=collector_width,
         pitch=pitch,
         surface_to_axis_offset=surface_to_axis_offset,
-        cross_axis_tilt=cross_axis_tilt,
+        cross_axis_slope=cross_axis_slope,
         shading_row_rotation=rotation_angle,
     ),
 )
@@ -126,11 +126,11 @@
         solar_azimuth,
         axis_azimuth,
         shaded_row_rotation=rotation_angle,
-        axis_tilt=axis_tilt,
+        axis_slope=axis_slope,
         collector_width=collector_width,
         pitch=pitch,
         surface_to_axis_offset=surface_to_axis_offset,
-        cross_axis_tilt=cross_axis_tilt,
+        cross_axis_slope=cross_axis_slope,
         shading_row_rotation=rotation_angle,
     ),
     # shaded fraction in the evening
@@ -139,11 +139,11 @@
         solar_azimuth,
         axis_azimuth,
         shaded_row_rotation=rotation_angle,
-        axis_tilt=axis_tilt,
+        axis_slope=axis_slope,
         collector_width=collector_width,
         pitch=pitch,
         surface_to_axis_offset=surface_to_axis_offset,
-        cross_axis_tilt=cross_axis_tilt,
+        cross_axis_slope=cross_axis_slope,
         shading_row_rotation=rotation_angle,
     ),
 )
@@ -157,11 +157,11 @@
         solar_azimuth,
         axis_azimuth,
         shaded_row_rotation=rotation_angle,
-        axis_tilt=axis_tilt,
+        axis_slope=axis_slope,
         collector_width=collector_width,
         pitch=pitch,
         surface_to_axis_offset=surface_to_axis_offset,
-        cross_axis_tilt=cross_axis_tilt,
+        cross_axis_slope=cross_axis_slope,
         shading_row_rotation=rotation_angle,
     ),
     0,  # no shaded fraction in the evening
diff --git a/docs/examples/solar-tracking/plot_discontinuous_tracking.py b/docs/examples/solar-tracking/plot_discontinuous_tracking.py
index f385675d57..fd8a03c500 100644
--- a/docs/examples/solar-tracking/plot_discontinuous_tracking.py
+++ b/docs/examples/solar-tracking/plot_discontinuous_tracking.py
@@ -26,7 +26,7 @@
 
 class DiscontinuousTrackerMount(pvsystem.SingleAxisTrackerMount):
     # inherit from SingleAxisTrackerMount so that we get the
-    # constructor and tracking attributes (axis_tilt etc) automatically
+    # constructor and tracking attributes (axis_slope etc) automatically
 
     def get_orientation(self, solar_zenith, solar_azimuth):
         # Different trackers update at different rates; in this example we'll
@@ -37,9 +37,9 @@ def get_orientation(self, solar_zenith, solar_azimuth):
 
         tracking_data_15min = tracking.singleaxis(
             zenith_subset, azimuth_subset,
-            self.axis_tilt, self.axis_azimuth,
+            self.axis_slope, self.axis_azimuth,
             self.max_angle, self.backtrack,
-            self.gcr, self.cross_axis_tilt
+            self.gcr, self.cross_axis_slope
         )
         # propagate the 15-minute positions to 1-minute stair-stepped values:
         tracking_data_1min = tracking_data_15min.reindex(solar_zenith.index,
diff --git a/docs/examples/solar-tracking/plot_single_axis_tracking.py b/docs/examples/solar-tracking/plot_single_axis_tracking.py
index 4f7d62cb80..72172630c1 100644
--- a/docs/examples/solar-tracking/plot_single_axis_tracking.py
+++ b/docs/examples/solar-tracking/plot_single_axis_tracking.py
@@ -34,7 +34,7 @@
 truetracking_angles = tracking.singleaxis(
     apparent_zenith=solpos['apparent_zenith'],
     solar_azimuth=solpos['azimuth'],
-    axis_tilt=0,
+    axis_slope=0,
     axis_azimuth=180,
     max_angle=90,
     backtrack=False,  # for true-tracking
@@ -62,7 +62,7 @@
     backtracking_angles = tracking.singleaxis(
         apparent_zenith=solpos['apparent_zenith'],
         solar_azimuth=solpos['azimuth'],
-        axis_tilt=0,
+        axis_slope=0,
         axis_azimuth=180,
         max_angle=90,
         backtrack=True,
diff --git a/docs/examples/solar-tracking/plot_single_axis_tracking_on_sloped_terrain.py b/docs/examples/solar-tracking/plot_single_axis_tracking_on_sloped_terrain.py
index b3a204ce69..7131513a71 100644
--- a/docs/examples/solar-tracking/plot_single_axis_tracking_on_sloped_terrain.py
+++ b/docs/examples/solar-tracking/plot_single_axis_tracking_on_sloped_terrain.py
@@ -14,8 +14,8 @@
 # calculating the backtracking angle requires knowledge of the relative spacing
 # of adjacent tracker rows. This example shows how the backtracking angle
 # changes based on a vertical offset between rows caused by sloped terrain.
-# It uses :py:func:`pvlib.tracking.calc_axis_tilt` and
-# :py:func:`pvlib.tracking.calc_cross_axis_tilt` to calculate the necessary
+# It uses :py:func:`pvlib.tracking.calc_axis_slope` and
+# :py:func:`pvlib.tracking.calc_cross_axis_slope` to calculate the necessary
 # array geometry parameters and :py:func:`pvlib.tracking.singleaxis` to
 # calculate the backtracking angles.
 #
@@ -97,20 +97,20 @@
 
 # compare the backtracking angle at various terrain slopes
 fig, ax = plt.subplots()
-for cross_axis_tilt in [0, 5, 10]:
+for cross_axis_slope in [0, 5, 10]:
     tracker_data = tracking.singleaxis(
         apparent_zenith=solpos['apparent_zenith'],
         solar_azimuth=solpos['azimuth'],
-        axis_tilt=0,  # flat because the axis is perpendicular to the slope
+        axis_slope=0,  # flat because the axis is perpendicular to the slope
         axis_azimuth=180,  # N-S axis, azimuth facing south
         max_angle=90,
         backtrack=True,
         gcr=gcr,
-        cross_axis_tilt=cross_axis_tilt)
+        cross_axis_slope=cross_axis_slope)
 
     # tracker rotation is undefined at night
     backtracking_position = tracker_data['tracker_theta'].fillna(0)
-    label = 'cross-axis tilt: {}°'.format(cross_axis_tilt)
+    label = 'cross-axis tilt: {}°'.format(cross_axis_slope)
     backtracking_position.plot(label=label, ax=ax)
 
 plt.legend()
@@ -141,14 +141,14 @@
 axis_azimuth = 180  # tracker axis is still N-S
 
 # calculate the tracker axis tilt, assuming that the axis follows the terrain:
-axis_tilt = tracking.calc_axis_tilt(slope_azimuth, slope_tilt, axis_azimuth)
+axis_slope = tracking.calc_axis_slope(slope_azimuth, slope_tilt, axis_azimuth)
 
 # calculate the cross-axis tilt:
-cross_axis_tilt = tracking.calc_cross_axis_tilt(slope_azimuth, slope_tilt,
-                                                axis_azimuth, axis_tilt)
+cross_axis_slope = tracking.calc_cross_axis_slope(slope_azimuth, slope_tilt,
+                                                axis_azimuth, axis_slope)
 
-print('Axis tilt:', '{:0.01f}°'.format(axis_tilt))
-print('Cross-axis tilt:', '{:0.01f}°'.format(cross_axis_tilt))
+print('Axis tilt:', '{:0.01f}°'.format(axis_slope))
+print('Cross-axis tilt:', '{:0.01f}°'.format(cross_axis_slope))
 
 # %%
 # And now we can pass use these values to generate the tracker curve as
@@ -157,18 +157,18 @@
 tracker_data = tracking.singleaxis(
     apparent_zenith=solpos['apparent_zenith'],
     solar_azimuth=solpos['azimuth'],
-    axis_tilt=axis_tilt,  # no longer flat because the terrain imparts a tilt
+    axis_slope=axis_slope,  # no longer flat because the terrain imparts a tilt
     axis_azimuth=axis_azimuth,
     max_angle=90,
     backtrack=True,
     gcr=gcr,
-    cross_axis_tilt=cross_axis_tilt)
+    cross_axis_slope=cross_axis_slope)
 
 backtracking_position = tracker_data['tracker_theta'].fillna(0)
 backtracking_position.plot()
 
 title_template = 'Axis tilt: {:0.01f}°   Cross-axis tilt: {:0.01f}°'
-plt.title(title_template.format(axis_tilt, cross_axis_tilt))
+plt.title(title_template.format(axis_slope, cross_axis_slope))
 plt.show()
 
 # %%
diff --git a/docs/sphinx/source/reference/tracking.rst b/docs/sphinx/source/reference/tracking.rst
index 4e85ffa3de..1cf67bab8f 100644
--- a/docs/sphinx/source/reference/tracking.rst
+++ b/docs/sphinx/source/reference/tracking.rst
@@ -7,6 +7,6 @@ Tracking
    :toctree: generated/
 
    tracking.singleaxis
-   tracking.calc_axis_tilt
-   tracking.calc_cross_axis_tilt
+   tracking.calc_axis_slope
+   tracking.calc_cross_axis_slope
    tracking.calc_surface_orientation
diff --git a/docs/sphinx/source/user_guide/extras/nomenclature.rst b/docs/sphinx/source/user_guide/extras/nomenclature.rst
index 6c6ad92514..1467b49bdd 100644
--- a/docs/sphinx/source/user_guide/extras/nomenclature.rst
+++ b/docs/sphinx/source/user_guide/extras/nomenclature.rst
@@ -44,10 +44,10 @@ There is a convention on consistent variable names throughout the library:
     bhi
         Beam/direct horizontal irradiance
 
-    cross_axis_tilt
+    cross_axis_slope
         Cross-axis tilt angle. [°]
         Consider two parallel rows of modules at different height;
-        ``cross_axis_tilt`` is the angle formed the line formed by the
+        ``cross_axis_slope`` is the angle formed the line formed by the
         intersection between the slope containing the tracker axes and a plane
         perpendicular to the tracker axes, and the horizontal plane.
         Cross-axis tilt is measured by using a right-handed convention.
@@ -55,8 +55,8 @@ There is a convention on consistent variable names throughout the library:
         will have a negative cross-axis tilt if the tracker axes plane slopes
         down to the east and positive cross-axis tilt if the tracker axes plane
         slopes up to the east.
-        Use :func:`~pvlib.tracking.calc_cross_axis_tilt` to calculate
-        ``cross_axis_tilt``
+        Use :func:`~pvlib.tracking.calc_cross_axis_slope` to calculate
+        ``cross_axis_slope``
 
     dhi
         Diffuse horizontal irradiance
diff --git a/docs/sphinx/source/whatsnew/v0.13.1.rst b/docs/sphinx/source/whatsnew/v0.13.1.rst
index 58bf5664a4..ff5089aa15 100644
--- a/docs/sphinx/source/whatsnew/v0.13.1.rst
+++ b/docs/sphinx/source/whatsnew/v0.13.1.rst
@@ -13,7 +13,17 @@ Deprecations
 * Deprecate :py:func:`~pvlib.modelchain.get_orientation`. (:pull:`2495`)
 * Rename parameter name ``aparent_azimuth`` to ``solar_azimuth`` in :py:func:`~pvlib.tracking.singleaxis`.
   (:issue:`2479`, :pull:`2480`)
-* Rename parameter ``cross_axis_slope`` to ``cross_axis_tilt`` in :py:func:`pvlib.shading.shaded_fraction1d`. (:issue:`2334`, :pull:`2543`)
+* Rename ``axis_tilt`` and ``cross_axis_tilt`` terms to ``axis_slope`` and ``cross_axis_slope`` all through the project. Affects:
+
+  - :py:func:`pvlib.shading.shaded_fraction1d` parameters ``cross_axis_tilt`` and ``axis_tilt``
+  - :py:func:`pvlib.shading.projected_solar_zenith_angle` parameter ``axis_tilt``
+  - :py:func:`pvlib.tracking.singleaxis` parameters ``cross_axis_tilt`` and ``axis_tilt``
+  - :py:func:`pvlib.tracking.calc_surface_orientation` parameter ``axis_tilt``
+  - :py:func:`!pvlib.tracking.calc_axis_tilt` function signature is renamed to :py:func:`pvlib.tracking.calc_axis_slope`
+  - :py:func:`!pvlib.tracking.calc_cross_axis_tilt` function signature is renamed to :py:func:`pvlib.tracking.calc_cross_axis_slope` and parameter ``axis_tilt``
+  - :py:class:`pvlib.pvsystem.SingleAxisTrackerMount` dataclass fields ``axis_tilt`` and ``cross_axis_tilt``
+
+  (:issue:`2334`, :pull:`2543`)
 
 Bug fixes
 ~~~~~~~~~
diff --git a/docs/sphinx/source/whatsnew/v0.8.0.rst b/docs/sphinx/source/whatsnew/v0.8.0.rst
index 86fb81574f..04e2d16765 100644
--- a/docs/sphinx/source/whatsnew/v0.8.0.rst
+++ b/docs/sphinx/source/whatsnew/v0.8.0.rst
@@ -110,14 +110,14 @@ Enhancements
 * Added ``racking_model``, ``module_type``, and ``temperature_model_parameters`` to
   :py:class:`~pvlib.pvsystem.PVSystem` and :py:class:`~pvlib.tracking.SingleAxisTracker`
   repr methods. (:issue:`1027`)
-* Added :py:func:`~pvlib.tracking.calc_axis_tilt` to calculate the
-  tracker axes tilt and :py:func:`~pvlib.tracking.calc_cross_axis_tilt` to
+* Added :py:func:`!~pvlib.tracking.calc_axis_tilt` to calculate the
+  tracker axes tilt and :py:func:`!~pvlib.tracking.calc_cross_axis_tilt` to
   calculate the cross-axis tilt, which is the angle, relative to horizontal, of
   the line formed by the intersection between the slope containing the tracker
   axes and a plane perpendicular to the tracker axes. (:pull:`823`)
 * Added ``cross_axis_tilt`` argument to :py:func:`~pvlib.tracking.singleaxis`
   and :py:func:`~pvlib.tracking.SingleAxisTracker` which defaults to zero. Use
-  :py:func:`~pvlib.tracking.calc_cross_axis_tilt` to calculate the cross-axis
+  :py:func:`!~pvlib.tracking.calc_cross_axis_tilt` to calculate the cross-axis
   tilt angle if necessary. (:pull:`823`)
 * Added ability for :py:func:`pvlib.soiling.hsu` to accept arbitrary time intervals. (:pull:`980`)
 * Added :py:func:`pvlib.temperature.fuentes` for cell temperature modeling. (:pull:`1037`)
diff --git a/pvlib/modelchain.py b/pvlib/modelchain.py
index 09e4434e84..992399ccab 100644
--- a/pvlib/modelchain.py
+++ b/pvlib/modelchain.py
@@ -1257,7 +1257,7 @@ def _prep_inputs_tracking(self):
             self.results.solar_position['azimuth'])
         self.results.tracking['surface_tilt'] = (
             self.results.tracking['surface_tilt']
-                .fillna(self.system.axis_tilt))
+                .fillna(self.system.axis_slope))
         self.results.tracking['surface_azimuth'] = (
             self.results.tracking['surface_azimuth']
                 .fillna(self.system.axis_azimuth))
diff --git a/pvlib/pvsystem.py b/pvlib/pvsystem.py
index 23ca1a934a..185c2d598e 100644
--- a/pvlib/pvsystem.py
+++ b/pvlib/pvsystem.py
@@ -8,6 +8,7 @@
 import io
 import itertools
 from pathlib import Path
+from warnings import warn
 import inspect
 from urllib.request import urlopen
 import numpy as np
@@ -16,7 +17,7 @@
 from dataclasses import dataclass
 from abc import ABC, abstractmethod
 from typing import Optional, Union
-from pvlib._deprecation import renamed_kwarg_warning
+from pvlib._deprecation import renamed_kwarg_warning, pvlibDeprecationWarning
 import pvlib  # used to avoid albedo name collision in the Array class
 from pvlib import (atmosphere, iam, inverter, irradiance,
                    singlediode as _singlediode, spectrum, temperature)
@@ -1431,10 +1432,13 @@ class SingleAxisTrackerMount(AbstractMount):
 
     Parameters
     ----------
-    axis_tilt : float, default 0
+    axis_slope : float, default 0
         The tilt of the axis of rotation (i.e, the y-axis defined by
         axis_azimuth) with respect to horizontal. [degrees]
 
+        .. versionchanged:: 0.13.1
+            Renamed from ``axis_tilt`` to ``axis_slope``.
+
     axis_azimuth : float, default 180
         A value denoting the compass direction along which the axis of
         rotation lies, measured east of north. [degrees]
@@ -1442,7 +1446,7 @@ class SingleAxisTrackerMount(AbstractMount):
     max_angle : float or tuple, default 90
         A value denoting the maximum rotation angle, in decimal degrees,
         of the one-axis tracker from its horizontal position (horizontal
-        if axis_tilt = 0). If a float is provided, it represents the maximum
+        if axis_slope = 0). If a float is provided, it represents the maximum
         rotation angle, and the minimum rotation angle is assumed to be the
         opposite of the maximum angle. If a tuple of (min_angle, max_angle) is
         provided, it represents both the minimum and maximum rotation angles.
@@ -1468,7 +1472,7 @@ class SingleAxisTrackerMount(AbstractMount):
         between the tracking axes has a gcr of 2/6=0.333. If gcr is not
         provided, a gcr of 2/7 is default. gcr must be <=1. [unitless]
 
-    cross_axis_tilt : float, default 0.0
+    cross_axis_slope : float, default 0.0
         The angle, relative to horizontal, of the line formed by the
         intersection between the slope containing the tracker axes and a plane
         perpendicular to the tracker axes. Cross-axis tilt should be specified
@@ -1476,8 +1480,11 @@ class SingleAxisTrackerMount(AbstractMount):
         azimuth of 180 degrees (heading south) will have a negative cross-axis
         tilt if the tracker axes plane slopes down to the east and positive
         cross-axis tilt if the tracker axes plane slopes up to the east. Use
-        :func:`~pvlib.tracking.calc_cross_axis_tilt` to calculate
-        `cross_axis_tilt`. [degrees]
+        :func:`~pvlib.tracking.calc_cross_axis_slope` to calculate
+        `cross_axis_slope`. [degrees]
+
+        .. versionchanged:: 0.13.1
+            Renamed from ``cross_axis_tilt`` to ``cross_axis_slope``.
 
     racking_model : str, optional
         Valid strings are ``'open_rack'``, ``'close_mount'``,
@@ -1493,23 +1500,89 @@ class SingleAxisTrackerMount(AbstractMount):
        The height above ground of the center of the module [m]. Used for
        the Fuentes cell temperature model.
     """
-    axis_tilt: float = 0.0
+    axis_slope: float = 0.0
     axis_azimuth: float = 0.0
     max_angle: Union[float, tuple] = 90.0
     backtrack: bool = True
     gcr: float = 2.0/7.0
-    cross_axis_tilt: float = 0.0
+    cross_axis_slope: float = 0.0
     racking_model: Optional[str] = None
     module_height: Optional[float] = None
 
+    # __init__, and properties getters and setters are explicit to deprecate
+    # field axis_tilt, renamed to axis_slope; and
+    # field cross_axis_tilt, renamed to cross_axis_slope; GH#2334 & GH#2543
+    @renamed_kwarg_warning(
+        since="0.13.1",
+        old_param_name="axis_tilt",
+        new_param_name="axis_slope",
+    )
+    @renamed_kwarg_warning(
+        since="0.13.1",
+        old_param_name="cross_axis_tilt",
+        new_param_name="cross_axis_slope",
+    )
+    def __init__(self, axis_slope=0.0, axis_azimuth=0.0, max_angle=90.0,
+                 backtrack=True, gcr=2.0/7.0, cross_axis_slope=0.0,
+                 racking_model: Optional[str] = None,
+                 module_height: Optional[float] = None):
+        self.axis_slope = axis_slope
+        self.axis_azimuth = axis_azimuth
+        self.max_angle = max_angle
+        self.backtrack = backtrack
+        self.gcr = gcr
+        self.cross_axis_slope = cross_axis_slope
+        self.racking_model = racking_model
+        self.module_height = module_height
+
+    @property
+    def axis_tilt(self):
+        warn(
+            "'axis_tilt' is deprecated since v0.13.1. "
+            "Use 'axis_slope' instead.",
+            pvlibDeprecationWarning,
+            stacklevel=2,
+        )
+        return self.axis_slope
+
+    @axis_tilt.setter
+    def axis_tilt(self, new_value):
+        warn(
+            "'axis_tilt' is deprecated since v0.13.1. "
+            "Use 'axis_slope' instead.",
+            pvlibDeprecationWarning,
+            stacklevel=2,
+        )
+        self.axis_slope = new_value
+
+    @property
+    def cross_axis_tilt(self):
+        warn(
+            "'cross_axis_tilt' is deprecated since v0.13.1. "
+            "Use 'cross_axis_slope' instead.",
+            pvlibDeprecationWarning,
+            stacklevel=2,
+        )
+        return self.cross_axis_slope
+
+    @cross_axis_tilt.setter
+    def cross_axis_tilt(self, new_value):
+        warn(
+            "'cross_axis_tilt' is deprecated since v0.13.1. "
+            "Use 'cross_axis_slope' instead.",
+            pvlibDeprecationWarning,
+            stacklevel=2,
+        )
+        self.cross_axis_slope = new_value
+
     def get_orientation(self, solar_zenith, solar_azimuth):
         # note -- docstring is automatically inherited from AbstractMount
         from pvlib import tracking  # avoid circular import issue
         tracking_data = tracking.singleaxis(
             solar_zenith, solar_azimuth,
-            self.axis_tilt, self.axis_azimuth,
+            self.axis_slope, self.axis_azimuth,
             self.max_angle, self.backtrack,
-            self.gcr, self.cross_axis_tilt
+            self.gcr, self.cross_axis_slope
         )
         return tracking_data
 
diff --git a/pvlib/shading.py b/pvlib/shading.py
index 7be2b62ca5..e6a096e9a1 100644
--- a/pvlib/shading.py
+++ b/pvlib/shading.py
@@ -236,15 +236,20 @@ def sky_diffuse_passias(masking_angle):
     return 1 - cosd(masking_angle/2)**2
 
 
+@renamed_kwarg_warning(
+    since="0.13.1",
+    old_param_name="axis_tilt",
+    new_param_name="axis_slope",
+)
 def projected_solar_zenith_angle(solar_zenith, solar_azimuth,
-                                 axis_tilt, axis_azimuth):
+                                 axis_slope, axis_azimuth):
     r"""
     Calculate projected solar zenith angle in degrees.
 
     This solar zenith angle is projected onto the plane whose normal vector is
-    defined by ``axis_tilt`` and ``axis_azimuth``. The normal vector is in the
+    defined by ``axis_slope`` and ``axis_azimuth``. The normal vector is in the
     direction of ``axis_azimuth`` (clockwise from north) and tilted from
-    horizontal by ``axis_tilt``. See Figure 5 in [1]_:
+    horizontal by ``axis_slope``. See Figure 5 in [1]_:
 
     .. figure:: ../../_images/Anderson_Mikofski_2020_Fig5.jpg
        :alt: Wire diagram of coordinates systems to obtain the projected angle.
@@ -259,8 +264,12 @@ def projected_solar_zenith_angle(solar_zenith, solar_azimuth,
         Sun's apparent zenith in degrees.
     solar_azimuth : numeric
         Sun's azimuth in degrees.
-    axis_tilt : numeric
+    axis_slope : numeric
         Axis tilt angle in degrees. From horizontal plane to array plane.
+
+        .. versionchanged:: 0.13.1
+            Renamed from ``axis_tilt`` to ``axis_slope``
+
     axis_azimuth : numeric
         Axis azimuth angle in degrees.
         North = 0°; East = 90°; South = 180°; West = 270°
@@ -294,14 +303,14 @@ def projected_solar_zenith_angle(solar_zenith, solar_azimuth,
     single-axis tracker:
 
     >>> rotation = projected_solar_zenith_angle(solar_zenith, solar_azimuth,
-    >>>                                         axis_tilt=0, axis_azimuth=180)
+    >>>                                         axis_slope=0, axis_azimuth=180)
 
     Calculate the projected zenith angle in a south-facing fixed tilt array
     (note: the ``axis_azimuth`` of a fixed-tilt row points along the length
     of the row):
 
     >>> psza = projected_solar_zenith_angle(solar_zenith, solar_azimuth,
-    >>>                                     axis_tilt=0, axis_azimuth=90)
+    >>>                                     axis_slope=0, axis_azimuth=90)
 
     References
     ----------
@@ -328,7 +337,7 @@ def projected_solar_zenith_angle(solar_zenith, solar_azimuth,
     sind_solar_zenith = sind(solar_zenith)
     cosd_axis_azimuth = cosd(axis_azimuth)
     sind_axis_azimuth = sind(axis_azimuth)
-    sind_axis_tilt = sind(axis_tilt)
+    sind_axis_slope = sind(axis_slope)
 
     # Sun's x, y, z coords
     sx = sind_solar_zenith * sind(solar_azimuth)
@@ -337,9 +346,9 @@ def projected_solar_zenith_angle(solar_zenith, solar_azimuth,
     # Eq. (4); sx', sz' values from sun coordinates projected onto surface
     sx_prime = sx * cosd_axis_azimuth - sy * sind_axis_azimuth
     sz_prime = (
-        sx * sind_axis_azimuth * sind_axis_tilt
-        + sy * sind_axis_tilt * cosd_axis_azimuth
-        + sz * cosd(axis_tilt)
+        sx * sind_axis_azimuth * sind_axis_slope
+        + sy * sind_axis_slope * cosd_axis_azimuth
+        + sz * cosd(axis_slope)
     )
     # Eq. (5); angle between sun's beam and surface
     theta_T = np.degrees(np.arctan2(sx_prime, sz_prime))
@@ -348,9 +357,13 @@ def projected_solar_zenith_angle(solar_zenith, solar_azimuth,
 
 @renamed_kwarg_warning(
     since="0.13.1",
-    old_param_name="cross_axis_slope",
-    new_param_name="cross_axis_tilt",
-    removal="0.15.0",
+    old_param_name="axis_tilt",
+    new_param_name="axis_slope",
+)
+@renamed_kwarg_warning(
+    since="0.13.1",
+    old_param_name="cross_axis_tilt",
+    new_param_name="cross_axis_slope",
 )
 def shaded_fraction1d(
     solar_zenith,
@@ -360,9 +373,9 @@ def shaded_fraction1d(
     *,
     collector_width,
     pitch,
-    axis_tilt=0,
+    axis_slope=0,
     surface_to_axis_offset=0,
-    cross_axis_tilt=0,
+    cross_axis_slope=0,
     shading_row_rotation=None,
 ):
     r"""
@@ -400,15 +413,23 @@ def shaded_fraction1d(
         is the ratio of the shadow over this value.
     pitch : numeric
         Axis-to-axis horizontal spacing of the row.
-    axis_tilt : numeric, default 0
+    axis_slope : numeric, default 0
         Tilt of the rows axis from horizontal. In degrees :math:`^{\circ}`.
+
+        .. versionchanged:: 0.13.1
+            Renamed from ``axis_tilt`` to ``axis_slope``
+
     surface_to_axis_offset : numeric, default 0
         Distance between the rotating axis and the collector surface.
         May be used to account for a torque tube offset.
-    cross_axis_tilt : numeric, default 0
+    cross_axis_slope : numeric, default 0
         Angle of the plane containing the rows' axes relative to
         horizontal. Right-handed rotation with respect to the rows axes.
-        See :term:`cross_axis_tilt`. In degrees :math:`^{\circ}`.
+        See :term:`cross_axis_slope`. In degrees :math:`^{\circ}`.
+
+        .. versionchanged:: 0.13.1
+            Renamed from ``cross_axis_tilt`` to ``cross_axis_slope``
+
     shading_row_rotation : numeric, optional
         Right-handed rotation of the row casting the shadow, with respect
         to the row axis. In degrees :math:`^{\circ}`.
@@ -438,7 +459,7 @@ def shaded_fraction1d(
     +------------------+----------------------------+                     |
     | :math:`\theta_2` | ``shaded_row_rotation``    | Degrees             |
     +------------------+----------------------------+ :math:`^{\circ}`    |
-    | :math:`\beta_c`  | ``cross_axis_tilt``        |                     |
+    | :math:`\beta_c`  | ``cross_axis_slope``       |                     |
     +------------------+----------------------------+---------------------+
     | :math:`p`        | ``pitch``                  | Any consistent      |
     +------------------+----------------------------+ length unit across  |
@@ -459,8 +480,8 @@ def shaded_fraction1d(
 
     >>> shaded_fraction1d(solar_zenith=80, solar_azimuth=135,
     ...     axis_azimuth=90, shaded_row_rotation=30, shading_row_rotation=30,
-    ...     collector_width=2, pitch=3, axis_tilt=0,
-    ...     surface_to_axis_offset=0.05, cross_axis_tilt=0)
+    ...     collector_width=2, pitch=3, axis_slope=0,
+    ...     surface_to_axis_offset=0.05, cross_axis_slope=0)
     0.47755694708090535
 
     **Fixed-tilt north-facing array on sloped terrain**
@@ -473,8 +494,8 @@ def shaded_fraction1d(
 
     >>> shaded_fraction1d(solar_zenith=80, solar_azimuth=75.5,
     ...     axis_azimuth=270, shaded_row_rotation=50, shading_row_rotation=30,
-    ...     collector_width=2.5, pitch=4, axis_tilt=10,
-    ...     surface_to_axis_offset=0.05, cross_axis_tilt=0)
+    ...     collector_width=2.5, pitch=4, axis_slope=10,
+    ...     surface_to_axis_offset=0.05, cross_axis_slope=0)
     0.793244836197256
 
     **N-S single-axis tracker on sloped terrain**
@@ -485,8 +506,8 @@ def shaded_fraction1d(
     tracker is higher than the west-most tracker).
 
     >>> shaded_fraction1d(solar_zenith=80, solar_azimuth=90, axis_azimuth=180,
-    ...     shaded_row_rotation=-30, collector_width=1.4, pitch=3, axis_tilt=0,
-    ...     surface_to_axis_offset=0.10, cross_axis_tilt=7)
+    ...     shaded_row_rotation=-30, collector_width=1.4, pitch=3,
+    ...     axis_slope=0, surface_to_axis_offset=0.10, cross_axis_slope=7)
     0.8242176864434579
 
     Note the previous example only is valid for the shaded fraction of the
@@ -500,8 +521,8 @@ def shaded_fraction1d(
     in the afternoon.
 
     >>> shaded_fraction1d(solar_zenith=80, solar_azimuth=270, axis_azimuth=180,
-    ...     shaded_row_rotation=30, collector_width=1.4, pitch=3, axis_tilt=0,
-    ...     surface_to_axis_offset=0.10, cross_axis_tilt=7)
+    ...     shaded_row_rotation=30, collector_width=1.4, pitch=3, axis_slope=0,
+    ...     surface_to_axis_offset=0.10, cross_axis_slope=7)
     0.018002567182254348
 
     You must switch the input/output depending on the
@@ -529,14 +550,14 @@ def shaded_fraction1d(
     projected_solar_zenith = projected_solar_zenith_angle(
         solar_zenith,
         solar_azimuth,
-        axis_tilt,
+        axis_slope,
         axis_azimuth,
     )
 
     # calculate repeated elements
     thetas_1_S_diff = shading_row_rotation - projected_solar_zenith
     thetas_2_S_diff = shaded_row_rotation - projected_solar_zenith
-    thetaS_rotation_diff = projected_solar_zenith - cross_axis_tilt
+    thetaS_rotation_diff = projected_solar_zenith - cross_axis_slope
 
     cos_theta_2_S_diff_abs = np.abs(cosd(thetas_2_S_diff))
 
@@ -556,7 +577,7 @@ def shaded_fraction1d(
             / collector_width
             * cosd(thetaS_rotation_diff)
             / cos_theta_2_S_diff_abs
-            / cosd(cross_axis_tilt)
+            / cosd(cross_axis_slope)
         )
     )
 
@@ -668,7 +689,7 @@ def direct_martinez(
     >>>     solar_zenith=80, solar_azimuth=180,
     >>>     axis_azimuth=90, shaded_row_rotation=25,
     >>>     collector_width=0.5, pitch=1, surface_to_axis_offset=0,
-    >>>     cross_axis_tilt=5.711, shading_row_rotation=50)
+    >>>     cross_axis_slope=5.711, shading_row_rotation=50)
     >>> # calculation of the number of shaded blocks
     >>> shaded_blocks = np.ceil(total_blocks*shaded_fraction)
     >>> # apply the Martinez power losses to the calculated shading
diff --git a/pvlib/tracking.py b/pvlib/tracking.py
index a30cc27822..5f261fc3eb 100644
--- a/pvlib/tracking.py
+++ b/pvlib/tracking.py
@@ -4,16 +4,26 @@
 from pvlib.tools import cosd, sind, tand, acosd, asind
 from pvlib import irradiance
 from pvlib import shading
-from pvlib._deprecation import renamed_kwarg_warning
+from pvlib._deprecation import renamed_kwarg_warning, deprecated
 
 
+@renamed_kwarg_warning(
+    since="0.13.1",
+    old_param_name="axis_tilt",
+    new_param_name="axis_slope",
+)
+@renamed_kwarg_warning(
+    since="0.13.1",
+    old_param_name="cross_axis_tilt",
+    new_param_name="cross_axis_slope",
+)
 @renamed_kwarg_warning(
     since='0.13.1',
     old_param_name='apparent_azimuth',
     new_param_name='solar_azimuth')
 def singleaxis(apparent_zenith, solar_azimuth,
-               axis_tilt=0, axis_azimuth=0, max_angle=90,
-               backtrack=True, gcr=2.0/7.0, cross_axis_tilt=0):
+               axis_slope=0, axis_azimuth=0, max_angle=90,
+               backtrack=True, gcr=2.0/7.0, cross_axis_slope=0):
     r"""
     Determine the rotation angle of a single-axis tracker when given particular
     solar zenith and azimuth angles.
@@ -28,7 +38,7 @@ def singleaxis(apparent_zenith, solar_azimuth,
     oriented skyward. Rotation angle ``tracker_theta`` is a right-handed
     rotation around the y-axis in the x, y, z coordinate system and indicates
     tracker position relative to horizontal. For example, if tracker
-    ``axis_azimuth`` is 180 (oriented south) and ``axis_tilt`` is zero, then a
+    ``axis_azimuth`` is 180 (oriented south) and ``axis_slope`` is zero, then a
     ``tracker_theta`` of zero is horizontal, a ``tracker_theta`` of 30 degrees
     is a rotation of 30 degrees towards the west, and a ``tracker_theta`` of
     -90 degrees is a rotation to the vertical plane facing east.
@@ -41,10 +51,13 @@ def singleaxis(apparent_zenith, solar_azimuth,
     solar_azimuth : float, 1d array, or Series
         Solar apparent azimuth angles in decimal degrees.
 
-    axis_tilt : float, default 0
+    axis_slope : float, default 0
         The tilt of the axis of rotation (i.e, the y-axis defined by
         ``axis_azimuth``) with respect to horizontal.
-        ``axis_tilt`` must be >= 0 and <= 90. [degrees]
+        ``axis_slope`` must be >= 0 and <= 90. [degrees]
+
+        .. versionchanged:: 0.13.1
+            Renamed from ``axis_tilt`` to ``axis_slope``.
 
     axis_azimuth : float, default 0
         A value denoting the compass direction along which the axis of
@@ -53,7 +66,7 @@ def singleaxis(apparent_zenith, solar_azimuth,
     max_angle : float or tuple, default 90
         A value denoting the maximum rotation angle, in decimal degrees,
         of the one-axis tracker from its horizontal position (horizontal
-        if axis_tilt = 0). If a float is provided, it represents the maximum
+        if axis_slope = 0). If a float is provided, it represents the maximum
         rotation angle, and the minimum rotation angle is assumed to be the
         opposite of the maximum angle. If a tuple of (min_angle, max_angle) is
         provided, it represents both the minimum and maximum rotation angles.
@@ -79,10 +92,13 @@ def singleaxis(apparent_zenith, solar_azimuth,
         has a ``gcr`` of 2/6=0.333. If ``gcr`` is not provided, a ``gcr`` of
         2/7 is default. ``gcr`` must be <=1.
 
-    cross_axis_tilt : float, default 0.0
+    cross_axis_slope : float, default 0.0
         Angle of the plane containing the rows' axes relative to
         horizontal. Right-handed rotation with respect to the rows axes.
-        See :term:`cross_axis_tilt`. In degrees :math:`^{\circ}`.
+        See :term:`cross_axis_slope`. In degrees :math:`^{\circ}`.
+
+        .. versionchanged:: 0.13.1
+            Renamed from ``cross_axis_tilt`` to ``cross_axis_slope``.
 
     Returns
     -------
@@ -100,8 +116,8 @@ def singleaxis(apparent_zenith, solar_azimuth,
 
     See also
     --------
-    pvlib.tracking.calc_axis_tilt
-    pvlib.tracking.calc_cross_axis_tilt
+    pvlib.tracking.calc_axis_slope
+    pvlib.tracking.calc_cross_axis_slope
     pvlib.tracking.calc_surface_orientation
 
     References
@@ -138,7 +154,7 @@ def singleaxis(apparent_zenith, solar_azimuth,
     # rotation to the west is positive. This is a right-handed rotation
     # around the tracker y-axis.
     omega_ideal = shading.projected_solar_zenith_angle(
-        axis_tilt=axis_tilt,
+        axis_slope=axis_slope,
         axis_azimuth=axis_azimuth,
         solar_zenith=apparent_zenith,
         solar_azimuth=solar_azimuth,
@@ -152,10 +168,10 @@ def singleaxis(apparent_zenith, solar_azimuth,
     if backtrack:
         # distance between rows in terms of rack lengths relative to cross-axis
         # tilt
-        axes_distance = 1/(gcr * cosd(cross_axis_tilt))
+        axes_distance = 1/(gcr * cosd(cross_axis_slope))
 
         # NOTE: account for rare angles below array, see GH 824
-        temp = np.abs(axes_distance * cosd(omega_ideal - cross_axis_tilt))
+        temp = np.abs(axes_distance * cosd(omega_ideal - cross_axis_slope))
 
         # backtrack angle using [1], Eq. 14
         with np.errstate(invalid='ignore'):
@@ -186,7 +202,7 @@ def singleaxis(apparent_zenith, solar_azimuth,
     tracker_theta = np.clip(tracker_theta, min_angle, max_angle)
 
     # Calculate auxiliary angles
-    surface = calc_surface_orientation(tracker_theta, axis_tilt, axis_azimuth)
+    surface = calc_surface_orientation(tracker_theta, axis_slope, axis_azimuth)
     surface_tilt = surface['surface_tilt']
     surface_azimuth = surface['surface_azimuth']
     aoi = irradiance.aoi(surface_tilt, surface_azimuth,
@@ -204,7 +220,12 @@ def singleaxis(apparent_zenith, solar_azimuth,
     return out
 
 
-def calc_surface_orientation(tracker_theta, axis_tilt=0, axis_azimuth=0):
+@renamed_kwarg_warning(
+    since="0.13.1",
+    old_param_name="axis_tilt",
+    new_param_name="axis_slope",
+)
+def calc_surface_orientation(tracker_theta, axis_slope=0, axis_azimuth=0):
     """
     Calculate the surface tilt and azimuth angles for a given tracker rotation.
 
@@ -212,13 +233,17 @@ def calc_surface_orientation(tracker_theta, axis_tilt=0, axis_azimuth=0):
     ----------
     tracker_theta : numeric
         Tracker rotation angle as a right-handed rotation around
-        the axis defined by ``axis_tilt`` and ``axis_azimuth``.  For example,
-        with ``axis_tilt=0`` and ``axis_azimuth=180``, ``tracker_theta > 0``
+        the axis defined by ``axis_slope`` and ``axis_azimuth``.  For example,
+        with ``axis_slope=0`` and ``axis_azimuth=180``, ``tracker_theta > 0``
         results in ``surface_azimuth`` to the West while ``tracker_theta < 0``
         results in ``surface_azimuth`` to the East. [degree]
-    axis_tilt : float, default 0
+    axis_slope : float, default 0
         The tilt of the axis of rotation with respect to horizontal.
-        ``axis_tilt`` must be >= 0 and <= 90.  [degree]
+        ``axis_slope`` must be >= 0 and <= 90.  [degree]
+
+        .. versionchanged:: 0.13.1
+            Renamed from ``axis_tilt`` to ``axis_slope``.
+
     axis_azimuth : float, default 0
         A value denoting the compass direction along which the axis of
         rotation lies. Measured east of north. [degree]
@@ -237,7 +262,7 @@ def calc_surface_orientation(tracker_theta, axis_tilt=0, axis_azimuth=0):
        July 2013. :doi:`10.2172/1089596`
     """
     with np.errstate(invalid='ignore', divide='ignore'):
-        surface_tilt = acosd(cosd(tracker_theta) * cosd(axis_tilt))
+        surface_tilt = acosd(cosd(tracker_theta) * cosd(axis_slope))
 
         # clip(..., -1, +1) to prevent arcsin(1 + epsilon) issues:
         azimuth_delta = asind(np.clip(sind(tracker_theta) / sind(surface_tilt),
@@ -259,13 +284,16 @@ def calc_surface_orientation(tracker_theta, axis_tilt=0, axis_azimuth=0):
     return out
 
 
-def calc_axis_tilt(slope_azimuth, slope_tilt, axis_azimuth):
+def calc_axis_slope(slope_azimuth, slope_tilt, axis_azimuth):
     """
     Calculate tracker axis tilt in the global reference frame when on a sloped
     plane. Axis tilt is the inclination of the tracker rotation axis with
     respect to horizontal, ranging from 0 degrees (horizontal axis) to 90
     degrees (vertical axis).
 
+    .. versionchanged:: 0.13.1
+        Renamed function ``calc_axis_tilt`` to ``calc_axis_slope``.
+
     Parameters
     ----------
     slope_azimuth : float
@@ -277,13 +305,13 @@ def calc_axis_tilt(slope_azimuth, slope_tilt, axis_azimuth):
 
     Returns
     -------
-    axis_tilt : float
+    axis_slope : float
         tilt of tracker [degrees]
 
     See also
     --------
     pvlib.tracking.singleaxis
-    pvlib.tracking.calc_cross_axis_tilt
+    pvlib.tracking.calc_cross_axis_slope
 
     Notes
     -----
@@ -297,8 +325,8 @@ def calc_axis_tilt(slope_azimuth, slope_tilt, axis_azimuth):
     """
     delta_gamma = axis_azimuth - slope_azimuth
     # equations 18-19
-    tan_axis_tilt = cosd(delta_gamma) * tand(slope_tilt)
-    return np.degrees(np.arctan(tan_axis_tilt))
+    tan_axis_slope = cosd(delta_gamma) * tand(slope_tilt)
+    return np.degrees(np.arctan(tan_axis_slope))
 
 
 def _calc_tracker_norm(ba, bg, dg):
@@ -354,8 +382,13 @@ def _calc_beta_c(v, dg, ba):
     return beta_c
 
 
-def calc_cross_axis_tilt(
-        slope_azimuth, slope_tilt, axis_azimuth, axis_tilt):
+@renamed_kwarg_warning(
+    since="0.13.1",
+    old_param_name="axis_tilt",
+    new_param_name="axis_slope",
+)
+def calc_cross_axis_slope(
+        slope_azimuth, slope_tilt, axis_azimuth, axis_slope):
     """
     Calculate the angle, relative to horizontal, of the line formed by the
     intersection between the slope containing the tracker axes and a plane
@@ -368,6 +401,9 @@ def calc_cross_axis_tilt(
     if the tracker axes plane slopes down to the east and positive cross-axis
     tilt if the tracker axes plane slopes down to the west.
 
+    .. versionchanged:: 0.13.1
+        Renamed function ``calc_cross_axis_tilt`` to ``calc_cross_axis_slope``.
+
     Parameters
     ----------
     slope_azimuth : float
@@ -378,13 +414,16 @@ def calc_cross_axis_tilt(
         [degrees]
     axis_azimuth : float
         direction of tracker axes projected on the horizontal [degrees]
-    axis_tilt : float
-        tilt of trackers relative to horizontal.  ``axis_tilt`` must be >= 0
+    axis_slope : float
+        tilt of trackers relative to horizontal.  ``axis_slope`` must be >= 0
         and <= 90. [degree]
 
+        .. versionchanged:: 0.13.1
+            Renamed from ``axis_tilt`` to ``axis_slope``.
+
     Returns
     -------
-    cross_axis_tilt : float
+    cross_axis_slope : float
         angle, relative to horizontal, of the line formed by the intersection
         between the slope containing the tracker axes and a plane perpendicular
         to the tracker axes [degrees]
@@ -392,7 +431,7 @@ def calc_cross_axis_tilt(
     See also
     --------
     pvlib.tracking.singleaxis
-    pvlib.tracking.calc_axis_tilt
+    pvlib.tracking.calc_axis_slope
 
     Notes
     -----
@@ -407,7 +446,21 @@ def calc_cross_axis_tilt(
     # delta-gamma, difference between axis and slope azimuths
     delta_gamma = axis_azimuth - slope_azimuth
     # equation 22
-    v = _calc_tracker_norm(axis_tilt, slope_tilt, delta_gamma)
+    v = _calc_tracker_norm(axis_slope, slope_tilt, delta_gamma)
     # equation 26
-    beta_c = _calc_beta_c(v, delta_gamma, axis_tilt)
+    beta_c = _calc_beta_c(v, delta_gamma, axis_slope)
     return np.degrees(beta_c)
+
+
+# allow deprecated names of calc_cross_axis_slope and calc_axis_slope
+calc_axis_tilt = deprecated(
+    since="0.13.1",
+    name="calc_axis_tilt",  # else it uses calc_axis_slope by introspection
+    alternative="pvlib.tracking.calc_axis_slope"
+)(calc_axis_slope)
+
+calc_cross_axis_tilt = deprecated(
+    since="0.13.1",
+    name="calc_cross_axis_tilt",  # else it uses calc_cross_axis_slope
+    alternative="pvlib.tracking.calc_cross_axis_slope"
+)(calc_cross_axis_slope)
diff --git a/tests/test_pvsystem.py b/tests/test_pvsystem.py
index b58f9fd9e4..364bef1dee 100644
--- a/tests/test_pvsystem.py
+++ b/tests/test_pvsystem.py
@@ -6,6 +6,7 @@
 import pandas as pd
 
 import pytest
+from pvlib._deprecation import pvlibDeprecationWarning
 from .conftest import assert_series_equal, assert_frame_equal
 from numpy.testing import assert_allclose
 import unittest.mock as mock
@@ -2368,9 +2369,9 @@ def fixed_mount():
 
 @pytest.fixture
 def single_axis_tracker_mount():
-    return pvsystem.SingleAxisTrackerMount(axis_tilt=10, axis_azimuth=170,
+    return pvsystem.SingleAxisTrackerMount(axis_slope=10, axis_azimuth=170,
                                            max_angle=45, backtrack=False,
-                                           gcr=0.4, cross_axis_tilt=-5)
+                                           gcr=0.4, cross_axis_slope=-5)
 
 
 def test_FixedMount_constructor(fixed_mount):
@@ -2384,8 +2385,8 @@ def test_FixedMount_get_orientation(fixed_mount):
 
 
 def test_SingleAxisTrackerMount_constructor(single_axis_tracker_mount):
-    expected = dict(axis_tilt=10, axis_azimuth=170, max_angle=45,
-                    backtrack=False, gcr=0.4, cross_axis_tilt=-5)
+    expected = dict(axis_slope=10, axis_azimuth=170, max_angle=45,
+                    backtrack=False, gcr=0.4, cross_axis_slope=-5)
     for attr_name, expected_value in expected.items():
         assert getattr(single_axis_tracker_mount, attr_name) == expected_value
 
@@ -2519,3 +2520,36 @@ def test_Array_temperature_missing_parameters(model, keys):
         array.temperature_model_parameters = params
         with pytest.raises(KeyError, match=match):
             array.get_cell_temperature(irrads, temps, winds, model)
+
+
+def test_SingleAxisTrackerMount_renamed_attributes_tilt_to_slope(
+    single_axis_tracker_mount,
+):  # renamed attributes tested here are
+    # axis_tilt -> axis_slope and cross_axis_tilt -> cross_axis_slope
+
+    # test constructor
+    with pytest.warns(pvlibDeprecationWarning, match="axis_slope"):
+        pvsystem.SingleAxisTrackerMount(axis_tilt=10, axis_azimuth=170,
+                                        max_angle=45, backtrack=False,
+                                        gcr=0.4, cross_axis_slope=-5)
+    with pytest.warns(pvlibDeprecationWarning, match="cross_axis_slope"):
+        pvsystem.SingleAxisTrackerMount(axis_slope=10, axis_azimuth=170,
+                                        max_angle=45, backtrack=False,
+                                        gcr=0.4, cross_axis_tilt=-5)
+    with (pytest.warns(pvlibDeprecationWarning, match="axis_slope"),
+          pytest.warns(pvlibDeprecationWarning, match="cross_axis_slope")):
+        pvsystem.SingleAxisTrackerMount(axis_tilt=10, axis_azimuth=170,
+                                        max_angle=45, backtrack=False,
+                                        gcr=0.4, cross_axis_tilt=-5)
+
+    # read values
+    with pytest.warns(pvlibDeprecationWarning, match="axis_slope"):
+        single_axis_tracker_mount.axis_tilt
+    with pytest.warns(pvlibDeprecationWarning, match="cross_axis_slope"):
+        single_axis_tracker_mount.cross_axis_tilt
+
+    # set values
+    with pytest.warns(pvlibDeprecationWarning, match="axis_slope"):
+        single_axis_tracker_mount.axis_tilt = 25.132
+    with pytest.warns(pvlibDeprecationWarning, match="cross_axis_slope"):
+        single_axis_tracker_mount.cross_axis_tilt = 15.657
diff --git a/tests/test_shading.py b/tests/test_shading.py
index a19917774b..de9e10179a 100644
--- a/tests/test_shading.py
+++ b/tests/test_shading.py
@@ -9,7 +9,6 @@
 from pvlib import shading
 from pvlib.tools import atand
 
-from .conftest import fail_on_pvlib_version
 from pvlib._deprecation import pvlibDeprecationWarning
 
 
@@ -118,7 +117,7 @@ def true_tracking_angle_and_inputs_NREL():
     # data from NREL 'Slope-Aware Backtracking for Single-Axis Trackers'
     # doi.org/10.2172/1660126 ; Accessed on 2023-11-06.
     tzinfo = timezone(timedelta(hours=-5))
-    axis_tilt_angle = 9.666  # deg
+    axis_slope_angle = 9.666  # deg
     axis_azimuth_angle = 195.0  # deg
     timedata = pd.DataFrame(
         columns=("Apparent Elevation", "Solar Azimuth", "True-Tracking"),
@@ -139,7 +138,7 @@ def true_tracking_angle_and_inputs_NREL():
         "2019-01-01T08", "2019-01-01T17", freq="1h", tz=tzinfo
     )
     timedata["Apparent Zenith"] = 90.0 - timedata["Apparent Elevation"]
-    return (axis_tilt_angle, axis_azimuth_angle, timedata)
+    return (axis_slope_angle, axis_azimuth_angle, timedata)
 
 
 @pytest.fixture
@@ -161,7 +160,7 @@ def projected_solar_zenith_angle_edge_cases():
             [  45,      45,     90,      180,   -135],
             [  45,     315,     90,      180,    135],
         ],
-        columns=["solar_zenith", "solar_azimuth", "axis_tilt", "axis_azimuth",
+        columns=["solar_zenith", "solar_azimuth", "axis_slope", "axis_azimuth",
                  "psza"],
     )
     return premises_and_result_matrix
@@ -172,12 +171,12 @@ def test_projected_solar_zenith_angle_numeric(
     projected_solar_zenith_angle_edge_cases
 ):
     psza_func = shading.projected_solar_zenith_angle
-    axis_tilt, axis_azimuth, timedata = true_tracking_angle_and_inputs_NREL
+    axis_slope, axis_azimuth, timedata = true_tracking_angle_and_inputs_NREL
     # test against data provided by NREL
     psz = psza_func(
         timedata["Apparent Zenith"],
         timedata["Solar Azimuth"],
-        axis_tilt,
+        axis_slope,
         axis_azimuth,
     )
     assert_allclose(psz, timedata["True-Tracking"], atol=1e-3)
@@ -185,19 +184,19 @@ def test_projected_solar_zenith_angle_numeric(
     psza = psza_func(
         timedata["Apparent Zenith"],
         timedata["Solar Azimuth"],
-        -axis_tilt,
+        -axis_slope,
         axis_azimuth - 180,
     )
     assert_allclose(psza, -timedata["True-Tracking"], atol=1e-3)
 
     # test edge cases
-    solar_zenith, solar_azimuth, axis_tilt, axis_azimuth, psza_expected = (
+    solar_zenith, solar_azimuth, axis_slope, axis_azimuth, psza_expected = (
         v for _, v in projected_solar_zenith_angle_edge_cases.items()
     )
     psza = psza_func(
         solar_zenith,
         solar_azimuth,
-        axis_tilt,
+        axis_slope,
         axis_azimuth,
     )
     assert_allclose(psza, psza_expected, atol=1e-9)
@@ -215,17 +214,17 @@ def test_projected_solar_zenith_angle_datatypes(
     cast_type, cast_func, true_tracking_angle_and_inputs_NREL
 ):
     psz_func = shading.projected_solar_zenith_angle
-    axis_tilt, axis_azimuth, timedata = true_tracking_angle_and_inputs_NREL
+    axis_slope, axis_azimuth, timedata = true_tracking_angle_and_inputs_NREL
     sun_apparent_zenith = timedata["Apparent Zenith"].iloc[0]
     sun_azimuth = timedata["Solar Azimuth"].iloc[0]
 
-    axis_tilt, axis_azimuth, sun_apparent_zenith, sun_azimuth = (
+    axis_slope, axis_azimuth, sun_apparent_zenith, sun_azimuth = (
         cast_func(sun_apparent_zenith),
         cast_func(sun_azimuth),
-        cast_func(axis_tilt),
+        cast_func(axis_slope),
         cast_func(axis_azimuth),
     )
-    psz = psz_func(sun_apparent_zenith, axis_azimuth, axis_tilt, axis_azimuth)
+    psz = psz_func(sun_apparent_zenith, axis_azimuth, axis_slope, axis_azimuth)
     assert isinstance(psz, cast_type)
 
 
@@ -261,7 +260,7 @@ def sf1d_premises_and_expected():
         ),
     )  # fmt: skip
 
-    test_data["cross_axis_tilt"] = atand(
+    test_data["cross_axis_slope"] = atand(
         (test_data["z_R"] - test_data["z_L"])
         / (test_data["x_L"] - test_data["x_R"])
     )
@@ -317,7 +316,7 @@ def test_shaded_fraction1d_unprovided_shading_row_rotation():
     test_data = pd.DataFrame(
         columns=[
             "shaded_row_rotation", "surface_to_axis_offset", "collector_width",
-            "solar_zenith", "cross_axis_tilt", "pitch", "solar_azimuth",
+            "solar_zenith", "cross_axis_slope", "pitch", "solar_azimuth",
             "axis_azimuth", "expected_sf",
         ],
         data=[
@@ -332,8 +331,7 @@ def test_shaded_fraction1d_unprovided_shading_row_rotation():
     assert_allclose(sf, expected_sf, atol=1e-2)
 
 
-@fail_on_pvlib_version("0.15.0")
-def test_shaded_fraction1d_renamed_cross_axis_slope2cross_axis_tilt():
+def test_shaded_fraction1d_renamed_cross_axis_tilt2cross_axis_slope():
     # Tests shaded_fraction1d with cross_axis_slope instead of cross_axis_tilt
     with pytest.warns(pvlibDeprecationWarning, match="cross_axis_slope"):
         shading.shaded_fraction1d(
@@ -344,7 +342,7 @@ def test_shaded_fraction1d_renamed_cross_axis_slope2cross_axis_tilt():
             collector_width=3,
             pitch=7,
             surface_to_axis_offset=0,
-            cross_axis_slope=0,
+            cross_axis_tilt=0,
         )
 
 
@@ -408,3 +406,19 @@ def test_direct_martinez(direct_martinez_Table2):
     test_data, power_losses_expected = direct_martinez_Table2
     power_losses = shading.direct_martinez(**test_data)
     assert_allclose(power_losses, power_losses_expected, atol=5e-3)
+
+
+def test_projected_solar_zenith_angle_renamed_axis_tilt_to_axis_slope():
+    with pytest.warns(pvlibDeprecationWarning, match="axis_slope"):
+        shading.projected_solar_zenith_angle(
+            10, 180, axis_tilt=20, axis_azimuth=30
+        )
+
+
+def test_shaded_fraction1d_renamed_tilt_to_slope():
+    with (pytest.warns(pvlibDeprecationWarning, match="axis_slope"),
+          pytest.warns(pvlibDeprecationWarning, match="cross_axis_slope")):
+        shading.shaded_fraction1d(
+            10, 10, 10, 10, collector_width=2, pitch=0.3,
+            axis_tilt=10, cross_axis_tilt=10
+        )
diff --git a/tests/test_tracking.py b/tests/test_tracking.py
index 8f3cb5824d..a0118870ae 100644
--- a/tests/test_tracking.py
+++ b/tests/test_tracking.py
@@ -7,6 +7,7 @@
 
 import pvlib
 from pvlib import tracking
+from pvlib._deprecation import pvlibDeprecationWarning
 from .conftest import TESTS_DATA_DIR, assert_frame_equal, assert_series_equal
 
 SINGLEAXIS_COL_ORDER = ['tracker_theta', 'aoi',
@@ -18,7 +19,7 @@ def test_solar_noon():
     apparent_zenith = pd.Series([10], index=index)
     apparent_azimuth = pd.Series([180], index=index)
     tracker_data = tracking.singleaxis(apparent_zenith, apparent_azimuth,
-                                       axis_tilt=0, axis_azimuth=0,
+                                       axis_slope=0, axis_azimuth=0,
                                        max_angle=90, backtrack=True,
                                        gcr=2.0/7.0)
 
@@ -34,7 +35,7 @@ def test_scalars():
     apparent_zenith = 10
     apparent_azimuth = 180
     tracker_data = tracking.singleaxis(apparent_zenith, apparent_azimuth,
-                                       axis_tilt=0, axis_azimuth=0,
+                                       axis_slope=0, axis_azimuth=0,
                                        max_angle=90, backtrack=True,
                                        gcr=2.0/7.0)
     assert isinstance(tracker_data, dict)
@@ -48,7 +49,7 @@ def test_arrays():
     apparent_zenith = np.array([10])
     apparent_azimuth = np.array([180])
     tracker_data = tracking.singleaxis(apparent_zenith, apparent_azimuth,
-                                       axis_tilt=0, axis_azimuth=0,
+                                       axis_slope=0, axis_azimuth=0,
                                        max_angle=90, backtrack=True,
                                        gcr=2.0/7.0)
     assert isinstance(tracker_data, dict)
@@ -63,7 +64,7 @@ def test_nans():
     apparent_azimuth = np.array([180, 180, np.nan])
     with np.errstate(invalid='ignore'):
         tracker_data = tracking.singleaxis(apparent_zenith, apparent_azimuth,
-                                           axis_tilt=0, axis_azimuth=0,
+                                           axis_slope=0, axis_azimuth=0,
                                            max_angle=90, backtrack=True,
                                            gcr=2.0/7.0)
     expect = {'tracker_theta': np.array([0, nan, nan]),
@@ -78,7 +79,7 @@ def test_nans():
     apparent_azimuth = pd.Series(apparent_azimuth)
     with np.errstate(invalid='ignore'):
         tracker_data = tracking.singleaxis(apparent_zenith, apparent_azimuth,
-                                           axis_tilt=0, axis_azimuth=0,
+                                           axis_slope=0, axis_azimuth=0,
                                            max_angle=90, backtrack=True,
                                            gcr=2.0/7.0)
     expect = pd.DataFrame(np.array(
@@ -95,7 +96,7 @@ def test_arrays_multi():
     # singleaxis should fail for num dim > 1
     with pytest.raises(ValueError):
         tracking.singleaxis(apparent_zenith, apparent_azimuth,
-                            axis_tilt=0, axis_azimuth=0,
+                            axis_slope=0, axis_azimuth=0,
                             max_angle=90, backtrack=True,
                             gcr=2.0/7.0)
     # uncomment if we ever get singleaxis to support num dim > 1 arrays
@@ -113,7 +114,7 @@ def test_azimuth_north_south():
     apparent_azimuth = pd.Series([90])
 
     tracker_data = tracking.singleaxis(apparent_zenith, apparent_azimuth,
-                                       axis_tilt=0, axis_azimuth=180,
+                                       axis_slope=0, axis_azimuth=180,
                                        max_angle=90, backtrack=True,
                                        gcr=2.0/7.0)
 
@@ -125,7 +126,7 @@ def test_azimuth_north_south():
     assert_frame_equal(expect, tracker_data)
 
     tracker_data = tracking.singleaxis(apparent_zenith, apparent_azimuth,
-                                       axis_tilt=0, axis_azimuth=0,
+                                       axis_slope=0, axis_azimuth=0,
                                        max_angle=90, backtrack=True,
                                        gcr=2.0/7.0)
 
@@ -138,7 +139,7 @@ def test_max_angle():
     apparent_zenith = pd.Series([60])
     apparent_azimuth = pd.Series([90])
     tracker_data = tracking.singleaxis(apparent_zenith, apparent_azimuth,
-                                       axis_tilt=0, axis_azimuth=0,
+                                       axis_slope=0, axis_azimuth=0,
                                        max_angle=45, backtrack=True,
                                        gcr=2.0/7.0)
 
@@ -154,7 +155,7 @@ def test_min_angle():
     apparent_zenith = pd.Series([60])
     apparent_azimuth = pd.Series([270])
     tracker_data = tracking.singleaxis(apparent_zenith, apparent_azimuth,
-                                       axis_tilt=0, axis_azimuth=0,
+                                       axis_slope=0, axis_azimuth=0,
                                        max_angle=(-45, 50), backtrack=True,
                                        gcr=2.0/7.0)
 
@@ -171,7 +172,7 @@ def test_backtrack():
     apparent_azimuth = pd.Series([90])
 
     tracker_data = tracking.singleaxis(apparent_zenith, apparent_azimuth,
-                                       axis_tilt=0, axis_azimuth=0,
+                                       axis_slope=0, axis_azimuth=0,
                                        max_angle=90, backtrack=False,
                                        gcr=2.0/7.0)
 
@@ -183,7 +184,7 @@ def test_backtrack():
     assert_frame_equal(expect, tracker_data)
 
     tracker_data = tracking.singleaxis(apparent_zenith, apparent_azimuth,
-                                       axis_tilt=0, axis_azimuth=0,
+                                       axis_slope=0, axis_azimuth=0,
                                        max_angle=90, backtrack=True,
                                        gcr=2.0/7.0)
 
@@ -195,12 +196,12 @@ def test_backtrack():
     assert_frame_equal(expect, tracker_data)
 
 
-def test_axis_tilt():
+def test_axis_slope():
     apparent_zenith = pd.Series([30])
     apparent_azimuth = pd.Series([135])
 
     tracker_data = tracking.singleaxis(apparent_zenith, apparent_azimuth,
-                                       axis_tilt=30, axis_azimuth=180,
+                                       axis_slope=30, axis_azimuth=180,
                                        max_angle=90, backtrack=True,
                                        gcr=2.0/7.0)
 
@@ -213,7 +214,7 @@ def test_axis_tilt():
     assert_frame_equal(expect, tracker_data)
 
     tracker_data = tracking.singleaxis(apparent_zenith, apparent_azimuth,
-                                       axis_tilt=30, axis_azimuth=0,
+                                       axis_slope=30, axis_azimuth=0,
                                        max_angle=90, backtrack=True,
                                        gcr=2.0/7.0)
 
@@ -230,7 +231,7 @@ def test_axis_azimuth():
     apparent_azimuth = pd.Series([90])
 
     tracker_data = tracking.singleaxis(apparent_zenith, apparent_azimuth,
-                                       axis_tilt=0, axis_azimuth=90,
+                                       axis_slope=0, axis_azimuth=90,
                                        max_angle=90, backtrack=True,
                                        gcr=2.0/7.0)
 
@@ -245,7 +246,7 @@ def test_axis_azimuth():
     apparent_azimuth = pd.Series([180])
 
     tracker_data = tracking.singleaxis(apparent_zenith, apparent_azimuth,
-                                       axis_tilt=0, axis_azimuth=90,
+                                       axis_slope=0, axis_azimuth=90,
                                        max_angle=90, backtrack=True,
                                        gcr=2.0/7.0)
 
@@ -265,7 +266,7 @@ def test_horizon_flat():
     solar_zenith = pd.Series(solar_zenith)
     # depending on platform and numpy versions this will generate
     # RuntimeWarning: invalid value encountered in > < >=
-    out = tracking.singleaxis(solar_zenith, solar_azimuth, axis_tilt=0,
+    out = tracking.singleaxis(solar_zenith, solar_azimuth, axis_slope=0,
                               axis_azimuth=180, backtrack=False, max_angle=180)
     expected = pd.DataFrame(np.array(
         [[ nan,  nan,  nan,  nan],
@@ -281,7 +282,7 @@ def test_horizon_tilted():
     solar_zenith = np.full_like(solar_azimuth, 45)
     solar_azimuth = pd.Series(solar_azimuth)
     solar_zenith = pd.Series(solar_zenith)
-    out = tracking.singleaxis(solar_zenith, solar_azimuth, axis_tilt=90,
+    out = tracking.singleaxis(solar_zenith, solar_azimuth, axis_slope=90,
                               axis_azimuth=180, backtrack=False, max_angle=180)
     expected = pd.DataFrame(np.array(
         [[-180.,  45.,   0.,  90.],
@@ -294,7 +295,7 @@ def test_horizon_tilted():
 def test_low_sun_angles():
     # GH 656, 824
     result = tracking.singleaxis(
-        apparent_zenith=80, apparent_azimuth=338, axis_tilt=30,
+        apparent_zenith=80, apparent_azimuth=338, axis_slope=30,
         axis_azimuth=180, max_angle=60, backtrack=True, gcr=0.35)
     expected = {
         'tracker_theta': np.array([60.0]),
@@ -305,9 +306,9 @@ def test_low_sun_angles():
         assert_allclose(expected[k], v)
 
 
-def test_calc_axis_tilt():
+def test_calc_axis_slope():
     # expected values
-    expected_axis_tilt = 2.239  # [degrees]
+    expected_axis_slope = 2.239  # [degrees]
     expected_side_slope = 9.86649274360294  # [degrees]
     expected = TESTS_DATA_DIR / 'singleaxis_tracker_wslope.csv'
     expected = pd.read_csv(expected, index_col='timestamp', parse_dates=True)
@@ -324,16 +325,16 @@ def test_calc_axis_tilt():
     # Note: GCR is relative to horizontal distance between rows
     gcr = 0.33292759  # GCR = length / horizontal_pitch = 1.64 / 5 / cos(9.86)
     # calculate tracker axis zenith
-    axis_tilt = tracking.calc_axis_tilt(
+    axis_slope = tracking.calc_axis_slope(
         slope_azimuth, slope_tilt, axis_azimuth=axis_azimuth)
-    assert np.isclose(axis_tilt, expected_axis_tilt)
+    assert np.isclose(axis_slope, expected_axis_slope)
     # calculate cross-axis tilt and relative rotation
-    cross_axis_tilt = tracking.calc_cross_axis_tilt(
-        slope_azimuth, slope_tilt, axis_azimuth, axis_tilt)
-    assert np.isclose(cross_axis_tilt, expected_side_slope)
+    cross_axis_slope = tracking.calc_cross_axis_slope(
+        slope_azimuth, slope_tilt, axis_azimuth, axis_slope)
+    assert np.isclose(cross_axis_slope, expected_side_slope)
     sat = tracking.singleaxis(
-        solpos.apparent_zenith, solpos.azimuth, axis_tilt, axis_azimuth,
-        max_angle, backtrack=True, gcr=gcr, cross_axis_tilt=cross_axis_tilt)
+        solpos.apparent_zenith, solpos.azimuth, axis_slope, axis_azimuth,
+        max_angle, backtrack=True, gcr=gcr, cross_axis_slope=cross_axis_slope)
     np.testing.assert_allclose(
         sat['tracker_theta'], expected['tracker_theta'], atol=1e-7)
     np.testing.assert_allclose(sat['aoi'], expected['aoi'], atol=1e-7)
@@ -362,28 +363,28 @@ def test_slope_aware_backtracking():
         ( 0.524817, 239.330401, 79.530, 5.490),
     ], columns=['ApparentElevation', 'SolarAzimuth',
                 'TrueTracking', 'Backtracking'])
-    expected_axis_tilt = 9.666
+    expected_axis_slope = 9.666
     expected_slope_angle = -2.576
     slope_azimuth, slope_tilt = 180.0, 10.0
     axis_azimuth = 195.0
-    axis_tilt = tracking.calc_axis_tilt(
+    axis_slope = tracking.calc_axis_slope(
         slope_azimuth, slope_tilt, axis_azimuth)
-    assert np.isclose(axis_tilt, expected_axis_tilt, rtol=1e-3, atol=1e-3)
-    cross_axis_tilt = tracking.calc_cross_axis_tilt(
-        slope_azimuth, slope_tilt, axis_azimuth, axis_tilt)
+    assert np.isclose(axis_slope, expected_axis_slope, rtol=1e-3, atol=1e-3)
+    cross_axis_slope = tracking.calc_cross_axis_slope(
+        slope_azimuth, slope_tilt, axis_azimuth, axis_slope)
     assert np.isclose(
-        cross_axis_tilt, expected_slope_angle, rtol=1e-3, atol=1e-3)
+        cross_axis_slope, expected_slope_angle, rtol=1e-3, atol=1e-3)
     sat = tracking.singleaxis(
         90.0-expected_data['ApparentElevation'], expected_data['SolarAzimuth'],
-        axis_tilt, axis_azimuth, max_angle=90.0, backtrack=True, gcr=0.5,
-        cross_axis_tilt=cross_axis_tilt)
+        axis_slope, axis_azimuth, max_angle=90.0, backtrack=True, gcr=0.5,
+        cross_axis_slope=cross_axis_slope)
     assert_series_equal(sat['tracker_theta'],
                         expected_data['Backtracking'].rename('tracker_theta'),
                         check_less_precise=True)
     truetracking = tracking.singleaxis(
         90.0-expected_data['ApparentElevation'], expected_data['SolarAzimuth'],
-        axis_tilt, axis_azimuth, max_angle=90.0, backtrack=False, gcr=0.5,
-        cross_axis_tilt=cross_axis_tilt)
+        axis_slope, axis_azimuth, max_angle=90.0, backtrack=False, gcr=0.5,
+        cross_axis_slope=cross_axis_slope)
     assert_series_equal(truetracking['tracker_theta'],
                         expected_data['TrueTracking'].rename('tracker_theta'),
                         check_less_precise=True)
@@ -397,7 +398,7 @@ def test_singleaxis_aoi_gh1221():
         tz='Etc/GMT+6')
     sp = loc.get_solarposition(dr)
     tr = pvlib.tracking.singleaxis(
-        sp['apparent_zenith'], sp['azimuth'], axis_tilt=90, axis_azimuth=180,
+        sp['apparent_zenith'], sp['azimuth'], axis_slope=90, axis_azimuth=180,
         max_angle=0.001, backtrack=False)
     fixed = pvlib.irradiance.aoi(90, 180, sp['apparent_zenith'], sp['azimuth'])
     fixed[np.isnan(tr['aoi'])] = np.nan
@@ -435,7 +436,7 @@ def test_calc_surface_orientation_kwargs():
     expected_tilts = np.array([22.2687445, 20.0, 22.2687445])
     expected_azimuths = np.array([152.72683041, 180.0, 207.27316959])
     out = tracking.calc_surface_orientation(rotations,
-                                            axis_tilt=20,
+                                            axis_slope=20,
                                             axis_azimuth=180)
     np.testing.assert_allclose(out['surface_tilt'], expected_tilts)
     np.testing.assert_allclose(out['surface_azimuth'], expected_azimuths)
@@ -450,11 +451,11 @@ def test_calc_surface_orientation_special():
     np.testing.assert_allclose(out['surface_tilt'], expected_tilts)
     np.testing.assert_allclose(out['surface_azimuth'], expected_azimuths)
 
-    # special case for axis_tilt
+    # special case for axis_slope
     rotations = np.array([-10, 0, 10])
     expected_tilts = np.array([90, 90, 90], dtype=float)
     expected_azimuths = np.array([350, 0, 10], dtype=float)
-    out = tracking.calc_surface_orientation(rotations, axis_tilt=90)
+    out = tracking.calc_surface_orientation(rotations, axis_slope=90)
     np.testing.assert_allclose(out['surface_tilt'], expected_tilts)
     np.testing.assert_allclose(out['surface_azimuth'], expected_azimuths)
 
@@ -471,3 +472,43 @@ def test_calc_surface_orientation_special():
         # in a modulo-360 sense.
         np.testing.assert_allclose(np.round(out['surface_azimuth'], 4) % 360,
                                    expected_azimuths, rtol=1e-5, atol=1e-5)
+
+
+def test_singleaxis_renamed_tilt_to_slope():
+    with (pytest.warns(pvlibDeprecationWarning, match="axis_slope"),
+          pytest.warns(pvlibDeprecationWarning, match="cross_axis_slope")):
+        tracking.singleaxis(
+            10, 10, axis_tilt=10, axis_azimuth=10, cross_axis_tilt=20
+        )
+
+
+def test_calc_surface_orientation_tilt_to_slope():
+    with pytest.warns(pvlibDeprecationWarning, match="axis_slope"):
+        tracking.calc_surface_orientation(10, axis_tilt=10, axis_azimuth=10)
+
+
+def test_deprecated_calc_axis_tilt():
+    # renamed to calc_axis_slope
+    with pytest.warns(pvlibDeprecationWarning, match="calc_axis_slope"):
+        tracking.calc_axis_tilt(slope_azimuth=1, slope_tilt=1, axis_azimuth=1)
+
+
+def test_deprecated_calc_cross_axis_tilt_and_param_tilt_to_slope():
+    # 1. calc_cross_axis_tilt renamed to calc_cross_axis_slope
+    # 2. parameter axis_tilt renamed to axis_slope
+
+    # just 1.
+    with pytest.warns(pvlibDeprecationWarning, match="calc_cross_axis_slope"):
+        tracking.calc_cross_axis_tilt(slope_azimuth=1, slope_tilt=1,
+                                      axis_azimuth=1, axis_slope=1)
+    # just 2.
+    with pytest.warns(pvlibDeprecationWarning, match="axis_slope"):
+        tracking.calc_cross_axis_slope(slope_azimuth=1, slope_tilt=1,
+                                       axis_azimuth=1, axis_tilt=1)
+    # both 1. and 2.
+    with (
+        pytest.warns(pvlibDeprecationWarning, match="axis_slope"),
+        pytest.warns(pvlibDeprecationWarning, match="calc_cross_axis_slope"),
+    ):  # somehow this order is important, the other way around fails
+        tracking.calc_cross_axis_tilt(slope_azimuth=1, slope_tilt=1,
+                                      axis_azimuth=1, axis_tilt=1)

From 27b24e743aa047fa2b5a64f919771e5eff8bc0d4 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Echedey=20Luis=20=C3=81lvarez?=
 <80125792+echedey-ls@users.noreply.github.com>
Date: Wed, 24 Sep 2025 11:42:04 +0200
Subject: [PATCH 11/15] Typo in v0.13.1 whatnew

---
 docs/sphinx/source/whatsnew/v0.13.1.rst | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/docs/sphinx/source/whatsnew/v0.13.1.rst b/docs/sphinx/source/whatsnew/v0.13.1.rst
index ff5089aa15..ad3f855ada 100644
--- a/docs/sphinx/source/whatsnew/v0.13.1.rst
+++ b/docs/sphinx/source/whatsnew/v0.13.1.rst
@@ -11,7 +11,7 @@ Breaking Changes
 Deprecations
 ~~~~~~~~~~~~
 * Deprecate :py:func:`~pvlib.modelchain.get_orientation`. (:pull:`2495`)
-* Rename parameter name ``aparent_azimuth`` to ``solar_azimuth`` in :py:func:`~pvlib.tracking.singleaxis`.
+* Rename parameter name ``apparent_azimuth`` to ``solar_azimuth`` in :py:func:`~pvlib.tracking.singleaxis`.
   (:issue:`2479`, :pull:`2480`)
 * Rename ``axis_tilt`` and ``cross_axis_tilt`` terms to ``axis_slope`` and ``cross_axis_slope`` all through the project. Affects:
 

From 3625a5a5aa545922404c87d313237318437ef668 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Echedey=20Luis=20=C3=81lvarez?=
 <80125792+echedey-ls@users.noreply.github.com>
Date: Wed, 24 Sep 2025 11:44:46 +0200
Subject: [PATCH 12/15] flake8 may forgive me

---
 .../plot_single_axis_tracking_on_sloped_terrain.py              | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/docs/examples/solar-tracking/plot_single_axis_tracking_on_sloped_terrain.py b/docs/examples/solar-tracking/plot_single_axis_tracking_on_sloped_terrain.py
index 7131513a71..64a03ce549 100644
--- a/docs/examples/solar-tracking/plot_single_axis_tracking_on_sloped_terrain.py
+++ b/docs/examples/solar-tracking/plot_single_axis_tracking_on_sloped_terrain.py
@@ -145,7 +145,7 @@
 
 # calculate the cross-axis tilt:
 cross_axis_slope = tracking.calc_cross_axis_slope(slope_azimuth, slope_tilt,
-                                                axis_azimuth, axis_slope)
+                                                  axis_azimuth, axis_slope)
 
 print('Axis tilt:', '{:0.01f}°'.format(axis_slope))
 print('Cross-axis tilt:', '{:0.01f}°'.format(cross_axis_slope))

From de940218bfb9c3a62b219e9d0c50ac16fa8fd49b Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Echedey=20Luis=20=C3=81lvarez?=
 <80125792+echedey-ls@users.noreply.github.com>
Date: Wed, 24 Sep 2025 11:55:24 +0200
Subject: [PATCH 13/15] whatsnew improvements

---
 docs/sphinx/source/whatsnew/v0.13.1.rst | 6 +++---
 docs/sphinx/source/whatsnew/v0.8.0.rst  | 6 +++---
 2 files changed, 6 insertions(+), 6 deletions(-)

diff --git a/docs/sphinx/source/whatsnew/v0.13.1.rst b/docs/sphinx/source/whatsnew/v0.13.1.rst
index 535c01805d..52375aaff8 100644
--- a/docs/sphinx/source/whatsnew/v0.13.1.rst
+++ b/docs/sphinx/source/whatsnew/v0.13.1.rst
@@ -13,14 +13,14 @@ Deprecations
 * Deprecate :py:func:`~pvlib.modelchain.get_orientation`. (:pull:`2495`)
 * Rename parameter name ``apparent_azimuth`` to ``solar_azimuth`` in :py:func:`~pvlib.tracking.singleaxis`.
   (:issue:`2479`, :pull:`2480`)
-* Rename ``axis_tilt`` and ``cross_axis_tilt`` terms to ``axis_slope`` and ``cross_axis_slope`` all through the project. Affects:
+* Rename ``axis_tilt`` and ``cross_axis_tilt`` to ``axis_slope`` and ``cross_axis_slope`` all through the project. Affects:
 
   - :py:func:`pvlib.shading.shaded_fraction1d` parameters ``cross_axis_tilt`` and ``axis_tilt``
   - :py:func:`pvlib.shading.projected_solar_zenith_angle` parameter ``axis_tilt``
   - :py:func:`pvlib.tracking.singleaxis` parameters ``cross_axis_tilt`` and ``axis_tilt``
   - :py:func:`pvlib.tracking.calc_surface_orientation` parameter ``axis_tilt``
-  - :py:func:`!pvlib.tracking.calc_axis_tilt` function signature is renamed to :py:func:`pvlib.tracking.calc_axis_slope`
-  - :py:func:`!pvlib.tracking.calc_cross_axis_tilt` function signature is renamed to :py:func:`pvlib.tracking.calc_cross_axis_slope` and parameter ``axis_tilt``
+  - :py:func:`!pvlib.tracking.calc_axis_tilt` function is renamed to :py:func:`~pvlib.tracking.calc_axis_slope`
+  - :py:func:`!pvlib.tracking.calc_cross_axis_tilt` function is renamed to :py:func:`~pvlib.tracking.calc_cross_axis_slope`, and its parameter ``axis_tilt``
   - :py:class:`pvlib.pvsystem.SingleAxisTrackerMount` dataclass fields ``axis_tilt`` and ``cross_axis_tilt``
 
   (:issue:`2334`, :pull:`2543`)
diff --git a/docs/sphinx/source/whatsnew/v0.8.0.rst b/docs/sphinx/source/whatsnew/v0.8.0.rst
index 04e2d16765..f3e9ae89be 100644
--- a/docs/sphinx/source/whatsnew/v0.8.0.rst
+++ b/docs/sphinx/source/whatsnew/v0.8.0.rst
@@ -110,14 +110,14 @@ Enhancements
 * Added ``racking_model``, ``module_type``, and ``temperature_model_parameters`` to
   :py:class:`~pvlib.pvsystem.PVSystem` and :py:class:`~pvlib.tracking.SingleAxisTracker`
   repr methods. (:issue:`1027`)
-* Added :py:func:`!~pvlib.tracking.calc_axis_tilt` to calculate the
-  tracker axes tilt and :py:func:`!~pvlib.tracking.calc_cross_axis_tilt` to
+* Added :py:func:`!pvlib.tracking.calc_axis_tilt` to calculate the
+  tracker axes tilt and :py:func:`!pvlib.tracking.calc_cross_axis_tilt` to
   calculate the cross-axis tilt, which is the angle, relative to horizontal, of
   the line formed by the intersection between the slope containing the tracker
   axes and a plane perpendicular to the tracker axes. (:pull:`823`)
 * Added ``cross_axis_tilt`` argument to :py:func:`~pvlib.tracking.singleaxis`
   and :py:func:`~pvlib.tracking.SingleAxisTracker` which defaults to zero. Use
-  :py:func:`!~pvlib.tracking.calc_cross_axis_tilt` to calculate the cross-axis
+  :py:func:`!pvlib.tracking.calc_cross_axis_tilt` to calculate the cross-axis
   tilt angle if necessary. (:pull:`823`)
 * Added ability for :py:func:`pvlib.soiling.hsu` to accept arbitrary time intervals. (:pull:`980`)
 * Added :py:func:`pvlib.temperature.fuentes` for cell temperature modeling. (:pull:`1037`)

From 7e5223435a952bbf27dd1ed93011728b4837014d Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Echedey=20Luis=20=C3=81lvarez?=
 <80125792+echedey-ls@users.noreply.github.com>
Date: Wed, 1 Oct 2025 18:20:32 +0200
Subject: [PATCH 14/15] move whatsnew entries

---
 docs/sphinx/source/whatsnew/v0.13.1.rst | 11 -----------
 docs/sphinx/source/whatsnew/v0.13.2.rst | 11 +++++++++++
 2 files changed, 11 insertions(+), 11 deletions(-)

diff --git a/docs/sphinx/source/whatsnew/v0.13.1.rst b/docs/sphinx/source/whatsnew/v0.13.1.rst
index 2e5d8fdd56..b056803b2b 100644
--- a/docs/sphinx/source/whatsnew/v0.13.1.rst
+++ b/docs/sphinx/source/whatsnew/v0.13.1.rst
@@ -10,17 +10,6 @@ Deprecations
 * Deprecate :py:func:`pvlib.modelchain.get_orientation`. (:pull:`2495`)
 * Rename parameter name ``apparent_azimuth`` to ``solar_azimuth`` in :py:func:`~pvlib.tracking.singleaxis`.
   (:issue:`2479`, :pull:`2480`)
-* Rename ``axis_tilt`` and ``cross_axis_tilt`` to ``axis_slope`` and ``cross_axis_slope`` all through the project. Affects:
-
-  - :py:func:`pvlib.shading.shaded_fraction1d` parameters ``cross_axis_tilt`` and ``axis_tilt``
-  - :py:func:`pvlib.shading.projected_solar_zenith_angle` parameter ``axis_tilt``
-  - :py:func:`pvlib.tracking.singleaxis` parameters ``cross_axis_tilt`` and ``axis_tilt``
-  - :py:func:`pvlib.tracking.calc_surface_orientation` parameter ``axis_tilt``
-  - :py:func:`!pvlib.tracking.calc_axis_tilt` function is renamed to :py:func:`~pvlib.tracking.calc_axis_slope`
-  - :py:func:`!pvlib.tracking.calc_cross_axis_tilt` function is renamed to :py:func:`~pvlib.tracking.calc_cross_axis_slope`, and its parameter ``axis_tilt``
-  - :py:class:`pvlib.pvsystem.SingleAxisTrackerMount` dataclass fields ``axis_tilt`` and ``cross_axis_tilt``
-
-  (:issue:`2334`, :pull:`2543`)
 
 Bug fixes
 ~~~~~~~~~
diff --git a/docs/sphinx/source/whatsnew/v0.13.2.rst b/docs/sphinx/source/whatsnew/v0.13.2.rst
index f649a93fd0..d4009ccd4e 100644
--- a/docs/sphinx/source/whatsnew/v0.13.2.rst
+++ b/docs/sphinx/source/whatsnew/v0.13.2.rst
@@ -6,6 +6,17 @@ v0.13.2 (Anticipated December, 2025)
 
 Breaking Changes
 ~~~~~~~~~~~~~~~~
+* Rename ``axis_tilt`` and ``cross_axis_tilt`` to ``axis_slope`` and ``cross_axis_slope`` all through the project. Affects:
+
+  - :py:func:`pvlib.shading.shaded_fraction1d` parameters ``cross_axis_tilt`` and ``axis_tilt``
+  - :py:func:`pvlib.shading.projected_solar_zenith_angle` parameter ``axis_tilt``
+  - :py:func:`pvlib.tracking.singleaxis` parameters ``cross_axis_tilt`` and ``axis_tilt``
+  - :py:func:`pvlib.tracking.calc_surface_orientation` parameter ``axis_tilt``
+  - :py:func:`!pvlib.tracking.calc_axis_tilt` function is renamed to :py:func:`~pvlib.tracking.calc_axis_slope`
+  - :py:func:`!pvlib.tracking.calc_cross_axis_tilt` function is renamed to :py:func:`~pvlib.tracking.calc_cross_axis_slope`, and its parameter ``axis_tilt``
+  - :py:class:`pvlib.pvsystem.SingleAxisTrackerMount` dataclass fields ``axis_tilt`` and ``cross_axis_tilt``
+
+  (:issue:`2334`, :pull:`2543`)
 
 
 Deprecations

From d8467bc43d376d5a096ae2b47b38d828ca64060c Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Echedey=20Luis=20=C3=81lvarez?=
 <80125792+echedey-ls@users.noreply.github.com>
Date: Wed, 1 Oct 2025 18:22:01 +0200
Subject: [PATCH 15/15] rm whatnew duplicated from merge entry

---
 docs/sphinx/source/whatsnew/v0.13.1.rst | 1 -
 1 file changed, 1 deletion(-)

diff --git a/docs/sphinx/source/whatsnew/v0.13.1.rst b/docs/sphinx/source/whatsnew/v0.13.1.rst
index b056803b2b..00e117b86b 100644
--- a/docs/sphinx/source/whatsnew/v0.13.1.rst
+++ b/docs/sphinx/source/whatsnew/v0.13.1.rst
@@ -6,7 +6,6 @@ v0.13.1 (September 24, 2025)
 
 Deprecations
 ~~~~~~~~~~~~
-* Deprecate :py:func:`~pvlib.modelchain.get_orientation`. (:pull:`2495`)
 * Deprecate :py:func:`pvlib.modelchain.get_orientation`. (:pull:`2495`)
 * Rename parameter name ``apparent_azimuth`` to ``solar_azimuth`` in :py:func:`~pvlib.tracking.singleaxis`.
   (:issue:`2479`, :pull:`2480`)