foot fault

Tennis term. According to the official International Tennis Federation (ITF) rules (as found on USTA.com):

A player (the server) commits a foot fault if after his feet are at rest but before he strikes the ball, either foot touches:

• the Court, including the baseline
• any part of the imaginary extension of the center mark
• beyond the imaginary extension of the outside edge of the sideline

The rules also state that a player must actually make an effort to hit the ball for a foot fault to occur. In other words, if a player's feet are placed illegally (as described above), but does not swing at the ball, it is not a foot fault.

A foot fault carries the same weight as any other fault (such as serving the ball into the net). Two consecutive faults of any type result in a double fault.

Foot faults are rather rare in professional tennis.