Tennis, game played with a racket and a ball by two (as in singles) or four (as in doubles) competitors, on a rectangular court with a net strung between the midpoints of the longer sides of the court. Tennis may be played indoors or outdoors. The game ranks as one of the most popular spectator and participation sports in the world, with fans and competitors in more than 100 countries. Originally called lawn tennis to distinguish it from the sport of court tennis, from which it was derived, the game is now commonly known as tennis. m3y20yx
The court is marked with white lines to indicate its dimensions and service areas. The court is 78 ft (23.8 m) long, divided into two equal sides by a net standing 3 ft (0.9 m) high at the center of the court. For singles the court is 27 ft (8.2 m) wide. For doubles the addition of alleys 4.5 ft (1.4 m) wide along the two longer sides increases the width to 36 ft (11 m). (For more detail, see accompanying diagram.) Courts may be of grass, clay, asphalt, concrete, wood, artificial grass, or other synthetic-materials. 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 Rackets were originally made of wood, but now virtually all rackets are made of such materials as aluminum or graphite, which are stronger and lighter than wood.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. Accordingly, first serve attempts usually have more velocity; second serves usually have greater accuracy and, sometimes, more spin. In preparation for returning serve, the receiver stands a certain distance behind the service box line, usually close to the baseline. In anticipation of a fast serve, many players move behind the baseline to provide more time to react. After the first point has been played, the service is made from the left-hand side of the court into the opponent's diagonally opposite service court. On each point thereafter the side from which service is made alternates until an entire game has been played. The opponent serves the next game, and the pattern of alternation of serve continues. In doubles, serves alternate between teams and also between players, so that an individual player will serve every fourth game.
After a successful serve the ball is hit back and forth until one player or side fails to return the ball successfully. A shot is unsuccessful when a player lets the ball bounce twice, drives it into the net, or hits it beyond the boundaries of the opposite side of the court. If the ball strikes the line of the court, it is considered in play. If, after hitting the net, a shot falls out of bounds on the opposite side of the court, it is considered out; if the ball falls in bounds in the opposite court, it is considered in play. When a shot is unsuccessful, the opponent scores a point.
Scoring is identical in the singles and doubles games. A tennis game, when not prolonged by a tie, is played to four points, designated by the terms 15, 30, 40, and game, with zero points being referred to by the term love (possibly derived from the French word for egg, l'oeuf, referring to the physical appearance of the number zero). A tie at 40 is called deuce. Because a game must be won by two points, play continues from deuce until one player leads by a margin of two points. After reaching deuce, the player who can win the game on the next point is said to have the advantage, while a subsequent tied score is always called deuce. (A system referred to as “no-ad” is sometimes employed in which the winner of the point following the first deuce wins the game.) In tennis competition, the score of the server is always given first. Typical scores at stages of a given tennis game might be “love-15” or “40-30.” The players or teams exchange sides after each odd-numbered game.
Players must win six games to win the set, but they must win by at least two games. Thus, if a set becomes tied at 5-5, at least 7 game victories are required to win the set. A tiebreaker is often employed if a set becomes tied at 6-6. A tiebreaker is generally played to 7 points, but because it too must be won by at least two points, it may be extended. The winner of a tiebreaker is recorded as having won the set 7-6, regardless of the point total achieved in the tiebreaker. Tennis matches are usually the best two out of three sets or the best three out of five sets.