Fix small grammar mistake.
diff --git a/Doc/glossary.rst b/Doc/glossary.rst
index 219a6ca..3af49fd 100644
--- a/Doc/glossary.rst
+++ b/Doc/glossary.rst
@@ -664,7 +664,7 @@
 
    statement
       A statement is part of a suite (a "block" of code).  A statement is either
-      an :term:`expression` or a one of several constructs with a keyword, such
+      an :term:`expression` or one of several constructs with a keyword, such
       as :keyword:`if`, :keyword:`while` or :keyword:`for`.
 
    struct sequence