Tennis is a sport usually played between two players (singles) or between two teams of two players each (doubles). Each player uses a racquet that is strung to strike a hollow rubber ball covered with felt 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" which has heavy connections to various field/lawn games as well as to the ancient game of real tennis. After its creation, tennis spread throughout the upper-class English-speaking population before spreading around the world.[1] Tennis is an Olympic sport and is played at all levels of society at all ages. Sports betting odds can be played by anyone who can hold a racket, including people in wheelchairs.

The rules of tennis have not changed much since the 1890s. Two exceptions are that from 1908 to 1960 the server had to keep one foot on the ground at all times, and then the adoption of the tie-break in the 1970s. A recent addition to professional tennis has been the adoption of electronic review technology coupled with a point challenge system, which allows a player to challenge the line (or chair) umpire's call of a point.

Players have unlimited opportunity to challenge, but once three incorrect challenges are made in a set, they cannot challenge again until the next set. If the set goes to a tie break, players are given one additional opportunity to challenge the call. This electronic review, currently called Hawk-Eye, is available at a limited number of high-level ATP and WTA tournaments.

Tennis is enjoyed by millions of recreational players and is also a hugely popular worldwide spectator sport, especially the four Grand Slam tournaments (also referred to as the "Majors"): the Australian Open played on hard courts, the French Open played on red clay courts, Wimbledon played on grass courts, and the US Open played also on hard courts.

The comprehensive rules promulgated in 1924 by the International Lawn Tennis Federation, now known as the International Tennis Federation, have remained remarkably stable in the ensuing eighty years, the one major change being the addition of the tie-break system designed by James Van Alen. That same year, tennis withdrew from the Olympics after the 1924 Games but returned 60 years later as a 21-and-under demonstration event in 1984. This reinstatement was credited by the efforts by the then ITF President Philippe Chatrier, ITF General Secretary David Gray and ITF Vice President Pablo Llorens, and support from IOC President Juan Antonio Samaranch. The success of the event was overwhelming and the IOC decided to reintroduce tennis as a full medal sport at Seoul in 1988.