Fix missing word.
diff --git a/Doc/library/os.rst b/Doc/library/os.rst
index 432de12..c8e47fc 100644
--- a/Doc/library/os.rst
+++ b/Doc/library/os.rst
@@ -1837,7 +1837,7 @@
Execute the command (a string) in a subshell. This is implemented by calling
the Standard C function :cfunc:`system`, and has the same limitations.
- Changes :data:`sys.stdin`, etc. are not reflected in the environment of the
+ Changes to :data:`sys.stdin`, etc. are not reflected in the environment of the
executed command.
On Unix, the return value is the exit status of the process encoded in the