Issue #12760: Refer to the new 'x' open mode as "exclusive creation" mode.
diff --git a/Doc/whatsnew/3.3.rst b/Doc/whatsnew/3.3.rst
index b2909f7..a60e585 100644
--- a/Doc/whatsnew/3.3.rst
+++ b/Doc/whatsnew/3.3.rst
@@ -427,8 +427,9 @@
io
--
-The :func:`~io.open` function has a new ``'x'`` mode that can be used to create
-a new file, and raise a :exc:`FileExistsError` if the file already exists.
+The :func:`~io.open` function has a new ``'x'`` mode that can be used to
+exclusively create a new file, and raise a :exc:`FileExistsError` if the file
+already exists. It is based on the C11 'x' mode to fopen().
(Contributed by David Townshend in :issue:`12760`)