There are several types of faults in tennis. For example, a ball will be called a fault (or " out " in English) when it does not fall within the boundaries of the court (the lines being located inside the court). The point is then awarded to the opponent. When the ball falls into the net, on the side of the player who hit the ball, the point is also awarded to the opponent, but it is not necessary to call a fault. The umpire should not signal a ball that falls into the net as a "fault".
The serve must be hit diagonally so that the ball falls into the service box. If the ball does not fall into the service box when the serve is served, the referee calls "fault", and the server must either serve a second ball if the fault occurs on the first serve, or award the point to the opponent if the fault occurs on the second serve. When both serves are faults (they do not fall into the service boxes, or fall into the net), it is called a "double fault". The point is then awarded to the receiver. When the ball hits the net rail and falls back into the service box where the player was supposed to serve, the referee calls " let " or " net ", the ball is not fault, and the player can play the serve again. On the other hand, if the server's ball hits the net rail and falls outside the service box, the ball is called a fault, and the player must either pass to his second ball, or award the point to the opponent depending on whether he hit a first or second ball.
A more complex fault concerns the server. In fact, to perform a valid service, it is necessary for the ball to be hit before the player crosses the baseline. Thus, when the player hits his serve, and already has a part of his body touching the ground inside the court or when the server "bites" the baseline at the time of his ball delivery, the service is refused. The player must then either hit a second service ball (if his fault was committed on the first ball), or award the point to the opponent if this fault occurs on the second ball. This fault, quite rarely reported because it is difficult to judge, is called a "foot fault". The "foot fault" is also valid on a lateral plane: the server must be on the correct side of the court so as to serve diagonally. If the server serves to the right, he must stand on the left side of the court (and vice versa) without being in the extension of the corridor
