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The serving rules are specified in chapter 2.6, 2.7, 2.8 & 2.9 in the ITTF Handbook 2020, the document from the International Table Tennis Federation
2.6. THE SERVE
2.6.1. Serve shall start with the ball resting freely on the open palm of the serve’s stationary free hand.
2.6.2. The serve shall then project the ball near vertically upwards, without imparting spin, so that it rises at least 16cm after leaving the palm of the free hand and then falls without touching anything before being struck.
2.6.3. As the ball is falling the serve shall strike it so that it touches first his or her court and then touches directly the receiver’s court. In doubles, the ball shall touch successively the right half court of serve and receiver.
2.6.4. From the start of service until it is struck, the ball shall be above the level of the playing surface and behind the serve’s end line, and it shall not be hidden from the receiver by the serve or his or her doubles partner or by anything they wear or carry
2.6.5. As soon as the ball has been projected, the serve’s free arm and hand shall be removed from the space between the ball and the net.
The space between the ball and the net is defined by the ball, the net and its indefinite upward extension.
2.6.6. It is the responsibility of the player to serve so that the umpire or the assistant umpire can be satisfied that he or she complies with the requirements of the Laws, and either may decide that a service is incorrect.
184.108.40.206. If either the umpire or the assistant umpire is not sure about the legality of a service he or she may, on the first occasion in a match, interrupt play and warn the serve; but any subsequent service by that player or his or her doubles partner which is not clearly legal shall be considered incorrect.
2.6.7. Exceptionally, the umpire may relax the requirements for a correct service where he or she is satisfied that compliance is prevented by physical disability.
2.7. THE RETURN
The ball, having been served or returned, shall be struck so that it touches the opponent’s court, either directly or after touching the net assembly
2.8. THE ORDER OF PLAY
2.8.1. In singles, the serve shall first make a service, the receiver shall then make a return and thereafter serve and receiver alternately shall each make a return.
2.8.2. In doubles, except as provided in 2.8.3, the serve shall first make a serve, the receiver shall then make a return, the partner of the serve shall then make a return, the partner of the receiver shall then make a return and thereafter each player in turn in that sequence shall make a return.
2.8.3 In doubles, when at least one player of a pair is in a wheelchair due to a physical disability, the serve shall first make a service, the receiver shall then make a return but thereafter either player of the disabled pair may make returns.
2.9.1 The rally shall be a let:
220.127.116.11 if in service the ball touches the net assembly, provided the serve is otherwise correct or the ball is obstructed by the receiver or his or her partner;
18.104.22.168. if the serve is delivered when the receiving player or pair is not ready, provided that neither the receiver nor his or her partner attempts to strike the ball;
22.214.171.124 if failure to make a serve or a return or otherwise to comply with the Laws is due to a disturbance outside the control of the player;
126.96.36.199 if play is interrupted by the umpire or assistant umpire;
188.8.131.52 if the receiver is in a wheelchair owing to a physical disability and in serve the ball, provided that the serve is otherwise correct,
184.108.40.206.1 after touching the receiver’s court returns in the direction of the net;
220.127.116.11.2 comes to rest on the receiver’s court;
18.104.22.168.3 in singles leaves the receiver’s court after touching it by either of its sidelines.
2.9.2 Play may be interrupted
22.214.171.124 to correct an error in the order of serving, receiving or ends;
126.96.36.199 to introduce the expedite system;
188.8.131.52 to warn or penalise a player or adviser;
184.108.40.206 because the conditions of play are disturbed in a way which could affect the outcome of the rally.
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