A tennis ball is hollow and composed of inflated rubber covered with a fabric made of wool and artificial fibers. It is between 2 1/2 and 2 5/8 in (6.35 and 6.67 cm) in diameter and weighs between 2 and 2 1/16 oz (57.7 and 58.5 g). Yellow and white balls are used in tournament competition and are the most common colors, although balls of other colors are manufactured.
There is no uniform design of tennis rackets, and their sizes and shapes vary. The general classifications, determined by the size of the racket head, are standard, midsize, oversize, and super oversize. In tournament play, the maximum length of a racket is 32 in (81.3 cm). The maximum width is 12.5 in (31.8 cm). The head of the racket may not exceed a length of 15.5 in (39.4 cm) and a width of 11.5 in (29.2 cm), and it is usually strung with resilient gut or nylon or other synthetic materials. There are no restrictions on weight. Rackets were originally made of wood, but now virtually all rackets are made of such materials as aluminum or graphite, which are stronger and lighter than wood. The racket handle is generally covered with a rubber or leather grip. Players usually wear lightweight clothing, traditionally white, and shoes with nonskid rubber soles.
A serve begins every point of a tennis match. The player who initiates the point is called the server, and the one who receives the ball is called the receiver. To serve, a player tosses the ball into the air and strikes it before it touches the ground, hitting it into the opponent's service area, known as the service box. Although players usually employ an overhand motion to serve, it is permissible to strike the ball underhanded.
The server delivers the ball from behind the baseline. His or her feet must remain outside the court until the ball is struck. On the first serve of a game, the server stands on the right side of the court and attempts to hit the ball into the service box on the diagonally opposite side of the court. Two tries are permitted for each service. If the ball first strikes any part of the opponent's court except the service box, or exits the court altogether, a fault is called. A fault is also called if the ball is served into the net, or if it strikes the net before hitting the opponent's court outside the service box or before exiting the court altogether. A foot fault is called if the server's foot enters the court before service is completed. After one fault a server may serve again. If both tries result in faults, a double fault is called, and the opponent wins the point. If the serve, on either try, touches the net and then falls into the diagonally opposite service box, a let is called, and the server is permitted to serve again. A valid serve that is not reached by the opponent is called an ace.
In general, the faster the serve, the more difficult it is to return. But a faster serve is also more difficult for the server to control.