Be consistent in the spelling of thread-safe(ty).
diff --git a/Doc/library/threading.rst b/Doc/library/threading.rst
index 3419e65..3e2e1e3 100644
--- a/Doc/library/threading.rst
+++ b/Doc/library/threading.rst
@@ -789,9 +789,9 @@
Importing in threaded code
--------------------------
-While the import machinery is thread safe, there are two key
-restrictions on threaded imports due to inherent limitations in the way
-that thread safety is provided:
+While the import machinery is thread-safe, there are two key restrictions on
+threaded imports due to inherent limitations in the way that thread-safety is
+provided:
* Firstly, other than in the main module, an import should not have the
side effect of spawning a new thread and then waiting for that thread in