The difference in horizontal location at the plate from a pitch that was thrown with no spin compared to the actual pitch that was thrown.
From the pitcher’s view a pitch with no spin will move in a straight line horizontally to the plate. A ball will also travel with no horizontal movement if the spin on the ball is perfectly 12 o’clock or 6 o’clock.
If the spin direction is between 12:01 and 5:59, the ball will have a horizontal break to the right.
If the spin direction is between 6:01 and 11:59, the ball will have a horizontal break to the left.