diff --git a/Doc/library/string.rst b/Doc/library/string.rst
--- a/Doc/library/string.rst
+++ b/Doc/library/string.rst
@@ -63,7 +63,8 @@
 
    String of ASCII characters which are considered printable.  This is a
    combination of :const:`digits`, :const:`ascii_letters`, :const:`punctuation`,
-   and :const:`whitespace`.
+   and :const:`whitespace`. Unlike :meth:`str.isprintable`; tab, linefeed,
+   return, formfeed, and vertical tab are also considered printable.
 
 
 .. data:: whitespace
@@ -761,4 +762,3 @@
    or ``None``, runs of whitespace characters are replaced by a single space
    and leading and trailing whitespace are removed, otherwise *sep* is used to
    split and join the words.
-