Tennis is a racquet sport played between either two players ("singles") or two teams of two players ("doubles"). Player(s) use a stringed racquet to strike a hollow rubber ball covered in felt over a net into the opponent's court. In some places, tennis is still called lawn tennis, to distinguish it from real tennis (also known as royal tennis or court tennis), an older form of the game that is played indoors on a very different kind of a court.

Tennis, released in 1989, was one of the first Game Boy games that could be played with two players via link cable simultaneously. Mario is the referee. Tennis is a video game released for the Nintendo Entertainment System in 1986. The concept of the game is very basic in that the player controls one person faced against an opponent CPU player. This game uses the same scoring system as "real-life" tennis. The game also features a doubles (2-player) option.

Balls, which are approved for play under the Rules of Tennis, The International Tennis Federation shall rule on the question of whether any ball or prototype complies with Appendix I or is otherwise approved, or not approved, for play. Such ruling may be taken on its own initiative, or upon application by any party with a bona fide interest therein, including any player, equipment manufacturer or National Association or members thereof. Such rulings and applications shall be made in accordance with the applicable Review and Hearing Procedures of the International Tennis Federation.