long tennis

              Tennis is a sport usually played between two players (single) or between two teams of two players each (double). Each player uses a racket that is strung to strike a hollow rubber ball covered with felt over a net into the opponent's court.

              The rules of tennis have not changed much since the 1890s. Two exceptions are that from 1908 to 1961 the server had to keep one foot on the ground at all times, and 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.

               The components of a tennis racquet are a handle and neck joining a roughly elliptical frame that holds a matrix of tightly pulled strings. For the first 100 years of the modern game, racquets were of wood and of standard size, and strings were of animal gut. Laminated wood construction yielded more strength in racquets used through most of the 20th century until first metal and then composites of carbon graphite, ceramics, and lighter metals such as titanium were introduced. These stronger materials enabled the production of oversize rackets that yielded yet more power. Meanwhile technology led to the use of synthetic strings that match the feel of gut yet with added durability.