Squash is a fast paced indoor court racquet sport whose evolution has been largely independent of any other sport, including racquetball, which bears some superficial similarities to squash. The central object of squash, which may be played in a singles or doubles format, is to play shots off the walled court with a racquet in such a fashion that the ball strikes the floor twice before the opponent can make a return.

Squash was first played in its modern form at Harrow, an English boy's school, in the years after 1850. Squash was descended from rackets, an outdoor walled game itself descended from early forms of tennis. Squash became a popular game at various English schools, and its appeal spread to North America and various parts of Europe in a short time. The first international squash competition took place between teams from the United States and Canada in 1922. The governing body of international squash, the World Squash Federation, (WSF) has over 120 national organization in its current membership.

As squash is actively played in over 150 countries, the WSF has made a concerted effort to secure the inclusion of squash as an Olympic Sport, without success. Squash is a medal sport in both the Commonwealth Games and the Pan American Games. The Professional Squash Association sanctions a vibrant professional squash series for both male and female competitors, with events staged throughout the world.

The squash court is a four walled rectangle, divided into sections through the placement of dividing lines that govern the placement of shots. A singles court is approximately 32 ft long and 21 ft wide (9.75 m by 6.4 m); the front wall is 15 ft high (4.57 m). Service boxes are laid out of the floor of the court, the area from which a player must make their serve. A doubles squash court is approximately 50% longer and 20% wider than the singles court.

The front wall has three lines marked across it. Closest to the floor of the court is the tin; approximately half way up the wall is the service line, and near the top of the wall is positioned the out line. A legal serve must strike the area between the tin and the service line, and land in the opponent's half of the court behind the service boxes. Once a legal serve has been made, both players may drive shots that strike the front wall between the tine and the out line. Players may use any of the walls to make shots, so long as the shot does not strike the wall above the out line.

There are two scoring systems used in squash. In the first system, known as the English system, points are only scored on the player's service. A typical match is the best of five games, with each game determined by the first player to reach nine points. The alternate scoring system, used most frequently in professional squash, awards a point to the successful player in every rally, with a game won at 11 points.

The most important pieces of squash equipment are the racquet and the ball. The racquets used today are invariably light weight (some are as light as 4 oz (110 g), with a very strong construction. The racquets are made from composite materials such as carbon fiber and are usually 27 in (68 cm) long. The materials used in the construction of the racquet create a degree of flex in the racquet that permits the player to transfer a greater measure of muscular power through the racquet into the ball on a stroke.

Men playing at squash championships (2005).

There are five different kinds of squash balls approved for various types of competition by the WSF. As a general proposition, the more experienced the players, the less lively the ball used will be; conversely, inexperienced players who have difficulty returning shots will enjoy the game more if the ball is livelier and is capable of bouncing higher from the court surface. The speed and resilience of the balls sanctioned by the WSF are classified by the color of the ball, ranging from "blue" (fast) to "double yellow" (super slow). At the highest levels of squash competition, the double yellow ball is the standard ball.

The ball characteristics dictate the warm-up between the players prior to a match. The warm-up shots of each player heats the ball to make it more responsive to shots made during the match.

During the course of play in the relatively close quarters of the squash court, if one of the payers is not able to reach a ball to make a shot due to the body position of the opponent, the hindered player is permitted to call "let," which, if legitimate, results in a replay of the serve.

As with other racquet sports, the fundamental tactic employed by a successful squash player is to seek control of the center of the court. In squash, given the location of the markings on the court, this desirable center position is called the "T." In this position, the player can respond more efficiently to any shot placed by the opponent.

Squash is a sport that requires continuous and effective movement. The successful squash player builds a strong aerobic base of fitness, to both support the player in a sport where the rallies are often demanding, as an aid to player recovery between serves. Squash is a sport that lends itself to a periodized approach to training, with a preseason focus upon building aerobic capacity, coupled with plyometric training to enhance explosive movement on the court, particularly in a lateral direction. The squash preseason may also include circuit training to develop overall muscular strength. The bending and turning motions associated with squash place a premium upon flexibility and optimal range of joint motion in every player. Comprehensive stretching programs are essential for this purpose in squash.

SEE ALSO Badminton; Handball; Racquetball; Tennis serve mechanics.