builtin -> built-in.
diff --git a/Doc/library/string.rst b/Doc/library/string.rst
index 3231d13..0b9b1fb 100644
--- a/Doc/library/string.rst
+++ b/Doc/library/string.rst
@@ -312,7 +312,7 @@
"Format specifications" are used within replacement fields contained within a
format string to define how individual values are presented (see
-:ref:`formatstrings`.) They can also be passed directly to the builtin
+:ref:`formatstrings`.) They can also be passed directly to the built-in
:func:`format` function. Each formattable type may define how the format
specification is to be interpreted.