lower case
diff --git a/Doc/library/io.rst b/Doc/library/io.rst
index 2684b27..c3ebe9a 100644
--- a/Doc/library/io.rst
+++ b/Doc/library/io.rst
@@ -43,7 +43,7 @@
 
 .. seealso::
    :mod:`sys`
-       Contains the standard IO streams: :data:`sys.stdin`, :data:`sys.stdout`,
+       contains the standard IO streams: :data:`sys.stdin`, :data:`sys.stdout`,
        and :data:`sys.stderr`.