#15694: Link discussion of file objects to glossary entry.
This is analogous to the link for `flie objects` in the description of
'open' that exists in the 2.7 docs, and adds a similar link to the
io docs.
Patch by Chris Jerdonek.
diff --git a/Doc/library/io.rst b/Doc/library/io.rst
index b71bfd4..62eaf6d 100644
--- a/Doc/library/io.rst
+++ b/Doc/library/io.rst
@@ -16,11 +16,15 @@
Overview
--------
-The :mod:`io` module provides Python's main facilities for dealing for various
-types of I/O. There are three main types of I/O: *text I/O*, *binary I/O*, *raw
-I/O*. These are generic categories, and various backing stores can be used for
-each of them. Concrete objects belonging to any of these categories will often
-be called *streams*; another common term is *file-like objects*.
+.. index::
+ single: file object; io module
+
+The :mod:`io` module provides Python's main facilities for dealing with various
+types of I/O. There are three main types of I/O: *text I/O*, *binary I/O*
+and *raw I/O*. These are generic categories, and various backing stores can
+be used for each of them. A concrete object belonging to any of these
+categories is called a :term:`file object`. Other common terms are *stream*
+and *file-like object*.
Independently of its category, each concrete stream object will also have
various capabilities: it can be read-only, write-only, or read-write. It can