diff --git a/geom.go b/geom.go
index ca8adf784..36bea1438 100644
--- a/geom.go
+++ b/geom.go
@@ -121,7 +121,7 @@ func (g *GeoM) Translate(tx, ty float64) {
 	g.ty += ty
 }
 
-// Rotate rotates the matrix by theta.
+// Rotate rotates the matrix clockwise by theta.
 // The unit is radian.
 func (g *GeoM) Rotate(theta float64) {
 	if theta == 0 {