Curveballs primarily break downwards, but can also break toward the pitcher's off hand to varying degrees. Unlike the fastball, the apex of the ball's flight path arc does not necessarily need to occur at the pitcher's release point, and often peaks shortly afterwards.

What way does a curve ball break?

Curveballs curve — or break downward — because of the spin imparted by the pitcher as he flings it toward home plate. The way Briggs explained it, the rotation of the seams creates a "whirlpool" of air around the ball and causes the pressure to be lower on one side.

Does the path of a curveball really curve?

It turns out that the path of a curveball really does curve as it flies through the air, making it unpredictable and hard to hit. Exploratorium staff physicist Paul Doherty explains where the curveball gets its curve.