Fix incorrect uses of a/an

tutorials/scripting/c_sharp/c_sharp_variant.rst

@@ -65,7 +65,7 @@ may be useful when the type of Variant is completely unknown. However, when poss
 specific conversions. ``Variant.Obj`` evaluates a ``switch`` on ``Variant.VariantType`` and it may
 not be necessary. Also, if the result is a value type, it is boxed.
 
-For example, if the potential for ``Variant.As<MyNode>()`` to throw a invalid cast exception isn't
+For example, if the potential for ``Variant.As<MyNode>()`` to throw an invalid cast exception isn't
 acceptable, consider using a ``Variant.As<GodotObject>() is MyNode n`` type pattern instead.
 
 .. note::

tutorials/scripting/change_scenes_manually.rst

@@ -118,7 +118,7 @@ access and integrity.
       access.
 
 There are also cases where one may wish to have many scenes present at the same
-time. Perhaps one is adding their own singleton at runtime, or preserving a
+time. Perhaps one is adding their own singleton at runtime, or preserving
 a scene's data between scene changes (adding the scene to the root node).
 
 .. tabs::

tutorials/scripting/evaluating_expressions.rst

@@ -9,7 +9,7 @@ An expression can be:
 
 - A mathematical expression such as ``(2 + 4) * 16/4.0``.
 - A built-in method call like ``deg_to_rad(90)``.
-- A method call on an user-provided script like ``update_health()``,
+- A method call on a user-provided script like ``update_health()``,
   if ``base_instance`` is set to a value other than ``null`` when calling
   :ref:`Expression.execute() <class_Expression_method_execute>`.
 

tutorials/scripting/gdextension/what_is_gdextension.rst

@@ -118,6 +118,6 @@ not compatible with Godot 3.x.
 
 GDExtension add-ons are also only compatible with engine builds that use the
 level of floating-point precision the extension was compiled for. This means
-that if you use a engine build with double-precision floats, the extension must
+that if you use an engine build with double-precision floats, the extension must
 also be compiled for double-precision floats. See
 :ref:`doc_large_world_coordinates` for details.