diff --git a/pointf.go b/pointf.go
index 0a397a7..d83180b 100644
--- a/pointf.go
+++ b/pointf.go
@@ -28,11 +28,16 @@ func (p PointF) To32() PointF32 {
 	return PointF32{float32(p.X), float32(p.Y)}
 }
 
-// Add adds q as a vector to p
+// Add adds q as a vector to p.
 func (p PointF) Add(q PointF) PointF {
 	return PointF{p.X + q.X, p.Y + q.Y}
 }
 
+// Sub subtracts q as a vector from p.
+func (p PointF) Sub(q PointF) PointF {
+	return PointF{p.X - q.X, p.Y - q.Y}
+}
+
 // AngleTo calculates the angle [0..2*Pi) from point p to point q.
 func (p PointF) AngleTo(q PointF) float64 {
 	a := math.Atan((p.Y - q.Y) / (p.X - q.X))