diff --git a/groff/math.tmac b/groff/math.tmac
index 4430c97..607b88d 100644
--- a/groff/math.tmac
+++ b/groff/math.tmac
@@ -18,6 +18,8 @@ define )> '{ \[ra] }'
 define ok '{ \[OK] }'
 define in '{ \[mo] }'
 define deg '{ \[de] }'
+define vel '{ roman v }'
+define freq '{ italic v }'
 define and '{ \[AN] }'
 define grad '{ \[gr] }'
 define aleph '{ \[Ah] }'