The ball is in play from the moment of the hit of the service authorized by the first referee.
The ball is out of play at the moment of the fault which is whistled by one of the referees, in the absence of a fault, at the moment of the whistle.
The ball is “in” if at any moment of its contact with the floor, some part of the ball touches the court, including the boundary lines.
The ball is “out” when:
8.4.1 all parts of the ball which contact the floor are completely outside the boundary lines;
8.4.2 it touches an object outside the court, the ceiling or a person out of play;
8.4.3 it touches the antennae, ropes, posts or the net itself outside the side bands;
8.4.4 it crosses the vertical plane of the net either partially or totally outside the crossing space, except in the case of Rule 10.1.2;
8.4.5 it crosses completely the lower space under the net (Diagram 5).