Curl or bend in association football is a definition for a spin on the ball which makes the ball move in a curved direction. When kicking the ball, the inside of the foot is often used to curl the ball, but this can also be done by using the outside of the foot. Similar to curl, the ball can also swerve in the air, without the spin on the ball which makes the ball curl.[1]
Curling or bending the ball is especially used in free kicks, shots from outside the penalty area and crosses. Differences between balls can affect the amount of swerve and curl: traditional leather footballs were too heavy to curl without great effort, whereas lighter modern footballs curl more easily.