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.
