diff --git a/Doc/library/functions.rst b/Doc/library/functions.rst
--- a/Doc/library/functions.rst
+++ b/Doc/library/functions.rst
@@ -726,12 +726,20 @@
 .. function:: locals()
 
    Update and return a dictionary representing the current local symbol table.
-   Free variables are returned by :func:`locals` when it is called in function
+   non-local names are returned by :func:`locals` when it is called in function
    blocks, but not in class blocks.
 
    .. note::
-      The contents of this dictionary should not be modified; changes may not
-      affect the values of local and free variables used by the interpreter.
+
+      The dictionary returned by locals() is an accurate snapshot of the local
+      namespace at the time it is called.  After the call returns, changes to
+      one may or may not be reflected in the other.  The dictionary may change
+      unpredictably after the call, and how it does is implementation-specific.
+      Holding a reference to the dictionary may produce surprising effects.  In
+      addition, the contents of this dictionary should not be modified; whether
+      changes affect the values of local and non-local variables used by the
+      interpreter is undefined and cannot not be relied upon to either happen
+      or not happen.
 
 .. function:: map(function, iterable, ...)