Be consistent in the spelling of thread-safe(ty).
diff --git a/Doc/library/multiprocessing.rst b/Doc/library/multiprocessing.rst
index 65c64e1..aa1e752 100644
--- a/Doc/library/multiprocessing.rst
+++ b/Doc/library/multiprocessing.rst
@@ -214,7 +214,7 @@
The ``'d'`` and ``'i'`` arguments used when creating ``num`` and ``arr`` are
typecodes of the kind used by the :mod:`array` module: ``'d'`` indicates a
double precision float and ``'i'`` indicates a signed integer. These shared
- objects will be process and thread safe.
+ objects will be process and thread-safe.
For more flexibility in using shared memory one can use the
:mod:`multiprocessing.sharedctypes` module which supports the creation of