diff -r 0e40091e9a24 Modules/itertoolsmodule.c
--- a/Modules/itertoolsmodule.c	Fri Jun 24 12:23:23 2016 -0700
+++ b/Modules/itertoolsmodule.c	Fri Jun 24 13:46:31 2016 -0700
@@ -170,7 +170,7 @@
 
 PyDoc_STRVAR(groupby_doc,
 "groupby(iterable[, keyfunc]) -> create an iterator which returns\n\
-(key, sub-iterator) grouped by each value of key(value).\n");
+(key, sub-iterator) grouped by consecutive occurrences of key(value).\n");
 
 static PyTypeObject groupby_type = {
     PyVarObject_HEAD_INIT(NULL, 0)