diff --git a/pep-0426.txt b/pep-0426.txt
index 3689546e9..60363905f 100644
--- a/pep-0426.txt
+++ b/pep-0426.txt
@@ -338,10 +338,10 @@ Examples::
 Provides-Extra (multiple use)
 -----------------------------
 
-A string containing the name of an optional feature. Must be printable
-ASCII, not containing whitespace, comma (,), or square brackets [].
-May be used to make a dependency conditional on whether the optional
-feature has been requested.
+A string containing the name of an optional feature or "extra" that may
+only be available when additional dependencies have been installed. Must
+be printable ASCII, not containing whitespace, comma (,), or square
+brackets [].
 
 See `Optional Features`_ for details on the use of this field.