Point (tennis)
A point is the smallest unit of scoring in tennis.
Play of a single point
The players (or teams) stand on opposite sides of the net. One player is designated the server, and the opposing player, or in doubles one of the opposing players, is the receiver. Serve alternates between the two halves of the court.
At the start of each point, the server stands behind his baseline, between the center mark and the sideline. The receiver may stand anywhere on his side of the net, usually behind the diagonally opposite service box.
A legal service starts a rally, in which the players alternate hitting the ball across the net. A legal return consists of the player or team hitting the ball exactly once before it has bounced twice or hit any fixtures. It then travels back over the net and bounces in the court on the opposite side. The first player or team to fail to make a legal return loses the point.
If a player hits the ball before it has bounced at all on his side of the net, the preceding return from his opponent is legal despite the ball not having bounced. Touching the net, hitting the ball before it has passed the net, touching the ball with anything other than the racquet, deliberately hitting the ball twice, and various other transgressions result in losing the point. In doubles, after the service and initial return either player may make any return; it is not permitted for both players on a team to hit the ball in the same return.
Because the lines are drawn just inside the courts, the ball is considered "in" if it touches any part of the relevant line. On clay courts the ball leaves an impression in the ground that can be checked; on grass courts a puff of chalk from the line indicates contact from the ball.
In an unumpired game, the players are to give each other the benefit of the doubt on line calls. In an umpired game it is the umpire or line umpire's duty to call the ball "out". The umpire may overrule a line umpire's call. In high-level tournaments, automatic equipment is increasingly used for line calls, especially for the serviceline.