Tennis is a game played between two players (singles) or between two teams of two players (doubles). Each player uses a strung racquet to strike a hollow rubber ball covered with felt (most of the time yellow, but can be any color or even two-tone) over a net into the opponent's court.

The modern game of tennis originated in the United Kingdom in the late 19th century as "lawn tennis" and had heavy connections to the ancient game of real tennis. After its creation, tennis spread throughout the upper-class English-speaking population before spreading around the world. Tennis is an Olympic sport and is played at all levels of society at all ages. The sport can be played by anyone who can hold a racket, including people in wheelchairs. In the United States, there is a collegiate circuit organized by the National Collegiate Athletics Association.

Except for the adoption of the tie-breaker in the 1970s, the rules of tennis have remained remarkably unchanged since the 1890s. A recent addition to tennis has been the adoption of "instant replay" technology coupled with a point challenge system which allows a player to challenge the official call of a point.

Along with its millions of players, millions of people worldwide follow tennis as a spectator sport, especially the four Grand Slam tournaments (sometimes referred to as the "majors"): Australian Open, French Open, Wimbledon, and the U.S. Open. The growth of tennis in Eastern Europe and the Far East has been especially notable in recent years.

Manner of play

The court

Tennis is played on a rectangular, flat surface, usually grass, clay, or a hardcourt of concrete and/or asphalt. The court is 78 feet (23.77 m) long, and its width is 27 feet (8.23 m) for singles matches and 36 ft (10.97 m) for doubles matches.[21] Additional clear space around the court is required in order for players to reach overrun balls. A net is stretched across the full width of the court, parallel with the baselines, dividing it into two equal ends. The net is 3 feet 6 inches (1.07 m) high at the posts and 3 feet (91.4 cm) high in the center

Lines

The lines that delineate the width of the court are called the baseline (furthest back) and the service line (middle of the court). The short mark in the center of each baseline is referred to as either the hash mark or the center mark. The outermost lines that make up the length are both called the doubles sideline. These are the boundaries used when doubles is being played. The area between the doubles sideline and the lines next to them is called the doubles alley, which is considered playable in doubles play. These lines next to the doubles sideline are the singles sidelines, and used as boundaries in singles play. The line that runs across the center of a player's side of the court is called the service line because the serve must be delivered into the area between the service line and the net on the receiving side. Despite its name, this is not where a player legally stands when making a serve. The line dividing the service line in two is called the center line or center service line. The boxes this center line creates are called the service boxes; depending on a player's position, he will have to hit the ball into one of these when serving. A ball is out only if none of it has hit the line upon its first bounce. All the lines are required to be 2 inches (51 mm) in width. The baseline can be up to 5 inches (130 mm) wide if so desired.

Play of a single point

The players (or teams) start 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. Service alternates between the two halves of the court. For each point, the server starts behind his baseline, between the center mark and the sideline. The receiver may start anywhere on their side of the net. When the receiver is ready, the server will serve, although the receiver must play to the pace of the server.

In a legal service, the ball travels over the net (without touching it) and into the diagonally opposite service box. If the ball hits the net but lands in the service box, this is a let service, which is void, and the server gets to retake that serve. The player can serve any number of let services in a point and they are always treated as voids and not as faults. Let services are somewhat unusual at recreational level and frequent at professional level. However, placing more than one let service in a single point takes a considerable amount of skill or luck. If the first service is otherwise faulty in any way, wide, long or not over the net, the serving player has a second attempt at service. There is also a "foot fault," which occurs when a player's foot touches the baseline or an extension of the center mark[22] before the ball is hit. If the second service is also faulty, this is a double fault, and the receiver wins the point. However, if the serve is in, it is considered a legal service.

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 except the net, provided that it still falls in the server's court. The ball 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.

Scoring

A tennis match comprises a number of sets, typically three for both men's and women's matches, the exception being at the major events (Wimbledon and the Australian, French and US Opens) where the men play best of five sets.[23] A set consists of a number of games, and games, in turn, consist of points.

A game consists of a sequence of points played with the same player serving, and is won by the first player to have won at least four points and at least two points more than his opponent. The running score of each game is described in a manner particular to tennis: scores of zero to three points are described as "love" (or zero), "fifteen," "thirty," and "forty" respectively. When at least three points have been scored by each side and the players have the same number of points, the score is "deuce." When at least three points have been scored by each side and a player has one more point than his opponent, the score of the game is "advantage" for the player in the lead. During informal games, "advantage" can also be called "ad in" or "ad out", depending on whether the serving player or receiving player is ahead, respectively. In tournament play, the chair umpire calls the point count (e.g., "fifteen-love") after each point. At the end of a game, the chair umpire also announces the winner of the game and the overall score.

A game point occurs in tennis whenever the player who is in the lead in the game needs only one more point to win the game. The terminology is extended to sets (set point), matches (match point), and even championships (championship point). For example, if the player who is serving has a score of 40-love, he has a triple game point (triple set point, etc.). Game points, set points, and match points are not part of official scoring and are not announced by the chair umpire in tournament play.

A break point occurs if the receiver, not the server, has a game point. It is of importance in professional tennis, since service breaks are rare enough to create a substantial advantage for the receiver in the men's game. The advantage to the server is much less in the women's game, but match analysts like to keep track of service breaks anyway. It may happen that the player who is in the lead in the game has more than one chance to score the winning point, even if his opponent should take the next point(s). For example, if the player who is serving has a score of 15-40, the receiver has a double break point. If the player in the lead wins any of the next two points, that player wins the game. Break points are not announced either.

A set consists of a sequence of games played with service alternating between games, ending when the count of games won meets certain criteria. Typically, a player wins a set when he wins at least six games and at least two games more than his opponent. When each player has won six games a tiebreaker is played. A tiebreaker, played under a separate set of rules, allows one player to win one more game and thus the set, to give a final set score of 7-6. Only in the final sets of matches at the Australian Open, the French Open, Wimbledon, Davis Cup, and Fed Cup are tie-breaks not played. A "love" set means that the loser of the set won zero games. For example if the score was 6 to 0, it would be 6 love. (See "tennis terminology" below for names given to unusual endings like the example here.) In tournament play, the chair umpire announces the winner of the set and the overall score.

Matches consist of an odd number of sets, the match winner being the player who wins more than half of the sets. The match ends as soon as this winning condition is met. Some matches may consist of five sets (the winner being the first to win three sets), while most matches are three sets (the winner being the first to win two sets). In tournament play, the chair umpire announces the end of the match with the well-known phrase "Game, set, match" followed by the winning team's name.

Rules variations

No-ad: The first player or doubles team to four points wins the game. One side does not have to win by two points. When the game score reaches three points each, the receiver chooses which side of the court (advantage court or deuce court) the service is to be delivered on the seventh and game-deciding point.
Pro set: Instead of playing multiple sets, players may play one "pro set". A pro set is first to 8 (or 10) games by a margin of two games, instead of first to 6. A 12-point tiebreaker is usually played when the score is 8-8 (or 10-10). These are often played with no-ad scoring. Match tie-break: This is sometimes played instead of a third set. This is played like a regular tie-break, but the winner must win ten points instead of seven. Match tie-breaks are used on the ATP and WTA tours for doubles and as a player's choice in USTA league play. Another, however informal, tennis format is called "Kiwi doubles", "Canadian doubles" or "cut-throat"[1]. This involves three players, with one person playing a doubles team. The single player gets to utilize the alleys normally reserved only for a doubles team. Conversely, the doubles team does *not* use the alleys when executing a shot. The scoring is the same as a regular game. This format is not sanctioned by any official body and is only played when a fourth player is not available for normal doubles.

"Australian doubles," another informal and unsanctioned form of tennis, is played with similar rules to the "Kiwi" style, only in this version, players rotate court position after each game. As such, each player plays doubles and singles over the course of a match, with the singles player always serving. Scoring styles vary, but one popular method is to assign a value of 2 points to each game, with the server taking both points if he or she holds serve, and the doubles team each taking one if they break.

Wheelchair tennis can be played by able-bodied players as well as people who require a wheelchair for mobility. An extra bounce is permitted. This rule makes it possible to have mixed wheelchair and able-bodied matches. It is possible for a doubles team to consist of a wheelchair player and an able-bodied player (referred to as "one-up, one-down"), or for a wheelchair player to play against an able-bodied player. In such cases, the extra bounce is permitted for the wheelchair users only.

Surface

There are three main types of court surfaces, with one less common surface. Depending on the materials used, each surface provides a difference in the speed and bounce of the ball, which in turn can affect the level of play of individual players. The three most common surfaces are:

Clay – red clay (used at the French Open), green clay (an example of which is Har-Tru and used mainly in the U.S.) Hard – examples are concrete, Plexicushion (used at the Australian Open), coated asphalt (used at the U.S. Open) Grass – used at Wimbledon
Indoor courts are also used so play can continue year-round. Common indoor surfaces are hard, carpet, and clay. Some players are more successful on certain surfaces and are known as "specialists" for that particular court.

Clay courts are considered a "slow" surface because the loose surface causes the ball to lose speed rapidly and bounce higher. This makes it more difficult for a player to hit an unreturnable shot (a "winner") because the opponent has more time to reach and return the ball. Line calls are easily reviewable on this type of court because the ball generally leaves a visible mark. Courts are swept between sets, and at the end of every match, to erase any marks from the previous set or match.

Hardcourts are generally considered to be a "fast" surface. However, there are many different types of hardcourts, and depending on the court's construction, the speed of the court can also be relatively slow. The typical hardcourt is characterised by low bounces and high ball speed, giving fast-serving and hard-hitting players an advantage.

Grass is considered to be a very "fast" surface. For many years, three of the four Grand Slam tournaments were held on grass. This changed when the Australian Open and the U.S. Open changed to hardcourts. Grass courts cause the ball to bounce low, or even skid, which generally keeps rallies short. This gives hard-serving and hard-hitting players an advantage because their shots are amplified on this surface. Grass also can cause unpredictable ball bounces. The bounce of the ball on grass courts can be altered by the health of the grass, the type of grass used, and how recently it has been mown. For that reason and low, fast bounces, a player's net game becomes more vital. This is because volleying a ball before it bounds avoids the need to deal with unpredictable bounces.

Carpet is found only indoors. It is made from a surface layer of "carpet" placed on top of a hard surface such as asphalt. The surface layer is thin and resiliant. Shots on carpet bounce like shots on an average hard court.

Professional and recreational players often wear different types of shoes depending on the playing surface. Shoes must have soles that grip the ground securely so that players can start and stop quickly. Where the shoes differ is how they grip the surface. For example, clay court shoes need to provide grip and traction while allowing the player to slide. Hardcourt shoes should emphasize grip, traction, and ankle support.

Officials

In most professional play and some amateur competition, there is an officiating head judge or chair umpire (usually referred to as the umpire), who sits in a raised chair to one side of the court. The umpire has absolute authority to make factual determinations. The umpire may be assisted by line judges, who determine whether the ball has landed within the required part of the court and who also call foot faults. There also may be a net judge who determines whether the ball has touched the net during service. In some tournaments, certain line judges, usually those who would be calling the serve, are replaced by electronic sensors that beep when an out call would have been made. In some open-tournament matches, players are allowed to challenge a limited number of close calls by means of instant replay. The U.S. Open, the Miami Masters, U.S. Open Series, and World Team Tennis started using a "challenge" system in 2006 and the Australian Open and Wimbledon introduced the system in 2007. This used the Hawk-Eye system and the rules were similar to those used in the NFL, where a player gets a limited number of instant-replay challenges per match/set. In clay-court matches, a call may be questioned by reference to the mark left by the ball's impact on the court surface.

The referee, who is usually located off the court, is the final authority about tennis rules. When called to the court by a player or team captain, the referee may overrule the umpire's decision if the tennis rules were violated (question of law) but may not change the umpire's decision on a question of fact. If, however, the referee is on the court during play, the referee may overrule the umpire's decision.

Ball boys or girls may be employed to retrieve balls, pass them to the players, and hand players their towels. They have no adjudicative role. In rare events (e.g., if they are hurt or if they have caused a hindrance), the umpire may ask them for a statement of what actually happened. The umpire may consider their statements when making a decision. In some leagues, especially junior leagues, players make their own calls, trusting each other to be honest. This is the case for many school and university level matches. However, the referee or referee's assistant can be called on court at a player's request, and the referee or assistant may change a player's call. In unofficiated matches, a ball is out only if the player entitled to make the call is sure that the ball is out.

Juniors

In tennis, a junior is a player under the age of 18 who is still legally protected by a parent or guardian. Players on the main adult tour who are under 18 must have documents signed by a parent or guardian. These players, however, are still eligible to play in junior tournaments.

The International Tennis Federation (ITF) conducts a junior tour that allows juniors to establish a world ranking and an Association of Tennis Professionals (ATP) or Women's Tennis Association (WTA) ranking. Most juniors who enter the international circuit do so by progressing through ITF, Satellite, Future, and Challenger tournaments before entering the main circuit. The latter three circuits also have adults competing in them. Some juniors, however, such as Australian Lleyton Hewitt and Frenchman Gael Monfils, have catapulted directly from the junior tour to the ATP tour by dominating the junior scene or by taking advantage of opportunities given to them to participate in professional tournaments.

In 2004, the ITF implemented a new rankings scheme to encourage greater participation in doubles, by combining two rankings (singles and doubles) into one combined tally. Junior tournaments do not offer prize money except for the Grand Slams, which are the most prestigious junior events. Juniors may earn income from tennis by participating in the Future, Satellite, or Challenger tours. Tournaments are broken up into different tiers offering different amounts of ranking points, culminating with Grade A.

Leading juniors are also allowed to participate for their nation in the Junior Fed Cup and Davis Cup competitions as well. To succeed in tennis often means having to begin playing at a young age. To facilitate and nurture a junior's growth in tennis, almost all tennis playing nations have developed a junior development system. Juniors develop their play through a range of tournaments on all surfaces, accommodating all different standards of play. Talented juniors may also receive sponsorships from governing bodies or private institutions.

Match play

A tennis match is intended to be continuous.[24] Stamina is a relevant factor, so arbitrary delays are not permitted. In most cases, service is required to occur no more than 20 (ITF events)[24] or 25 (ATP and WTA events) seconds after the end of the previous point. This is increased to 90 seconds when the players change ends (after every odd-numbered games), and a 120 second break is permitted between sets. Other than this, breaks are permitted only when forced by events beyond the players' control, such as rain, damaged footwear, damaged racquet, or the need to retrieve an errant ball. Should a player be determined to be stalling repeatedly, the chair umpire may initially give a warning followed by subsequent penalties of "point," "game," and default of the match for the player who is consistently taking longer than the allowed time limit.

In the event of a rain delay or other such proponent, the match must be resumed at a later time. On junior professional circuits the matches are to be resumed at the score which was at the time of the delay. However, as per new revisions beginning with the 2006 Australian Open, the ATP and WTA govern different regulations regarding delays; in the event of a rain delay, the match will resume while only the end of the previously completed set before the delay is official.

Balls wear out quickly in serious play and, therefore, in ATP and WTA tournaments, they are changed after every nine games with the first change occurring after only seven games, because the first set of balls is also used for the pre-match warm-up.However, in ITF serious tournaments like Fed Cup the balls are changed in a 9-11 style.[citation needed] Continuity of the balls' condition is considered part of the game,[citation needed] so if a re-warm-up is required after an extended break in play (usually due to rain), then the re-warm-up is done using a separate set of balls, and use of the match balls is resumed only when play resumes.

It has recently been proposed to allow coaching on court during a match on a limited basis.[citation needed] Also, technological review of official calls made its debut in a major tournament at the 2006 U.S. Open