Use sentence case in section titles consistently
diff --git a/Doc/reference/expressions.rst b/Doc/reference/expressions.rst
index 6ef4443..2396622 100644
--- a/Doc/reference/expressions.rst
+++ b/Doc/reference/expressions.rst
@@ -1161,7 +1161,7 @@
 'foo'`` yields ``False``, not ``''``.)
 
 
-Conditional Expressions
+Conditional expressions
 =======================
 
 .. index::