badminton (bădˈmĭntən) [key], game played by volleying a shuttlecock (called a "bird")—a small, cork hemisphere to which feathers are attached—over a net. Light, gut-strung rackets are used. Badminton, which is generally similar to tennis, is played by two or four persons. A badminton court for singles play measures 17 ft (5.18 m) by 44 ft (13.40 m) and for doubles 20 ft (6.10 m) by 44 ft (13.40 m). The net is 5 ft (1.52 m) high at the center and 5 ft 1 in. (1.55 m) at the posts. The game probably originated in India (where it was called poona), although it may have been known earlier in China. It was popular in the 1870s in England, taking its name from Badminton, the Gloucestershire estate of the duke of Beaufort. The game was introduced into the United States in the 1890s and grew in popularity in the 1930s. The International Badminton Association (founded 1934) sponsors the Thomas Cup for men's teams and the Woer Cup for women's teams, the world championships of badminton. Badminton has been an official Olympic sport since 1992.