Add more entries to the glossary.

Written by Jeff Wheeler for GHOP.
diff --git a/Doc/library/codecs.rst b/Doc/library/codecs.rst
index 5bab2af..c6dc0a3 100644
--- a/Doc/library/codecs.rst
+++ b/Doc/library/codecs.rst
@@ -1119,9 +1119,9 @@
 |                    |                           |                | all conversions. Can be   |
 |                    |                           |                | used as the system        |
 |                    |                           |                | encoding if no automatic  |
-|                    |                           |                | coercion between byte and |
-|                    |                           |                | Unicode strings is        |
-|                    |                           |                | desired.                  |
+|                    |                           |                | :term:`coercion` between  |
+|                    |                           |                | byte and Unicode strings  |
+|                    |                           |                | is desired.               |
 +--------------------+---------------------------+----------------+---------------------------+
 | unicode_escape     |                           | Unicode string | Produce a string that is  |
 |                    |                           |                | suitable as Unicode       |