ennis is a game which opposing players-one or two on each side-use rackets to hit a ball back and forth over a net. The game is played on a flat surface called a court. Each player tries to score points by hitting the ball so that the opposing player or players cannot return it over the net and inside the court.
             Tennis may be played indoors or outdoors. If two people play, the game is called singles. If four people play, it is called doubles. In most singles and doubles matches, men play men and women play women. In mixed doubles, a man and woman play on each side.
             The Court is a rectangle divided into halves by a net stretched across the middle. The net measures 3 feet high at the center and 3 1/2 feet high at the side posts that support it. The court is 78 feet long. The singles court measures 27 feet wide. The doubles court is 4 1/2 feet wider on each side. The most popular surfaces for outdoor courts are asphalt, clay, and concrete.
             Tennis Balls are hollow. They are made of rubber and covered with a felt fabric woven of Dacron, nylon, and wool. A tennis ball must have a diameter of more than 2 1/2 inches but less than 2 5/8 inches. It must weigh more than 2 ounces but less than 2 1/16 ounces. Balls used in tournaments may be either white or yellow.
             Before they begin to play tennis, the players must decide who serves first and which end of the court each player or team will defend. Most players make these decisions by means of a racket "toss". For example, they may use the manufacturer's markings on one side of a racket handle as "heads" and on the other side as "tails". One player stands the racket upright on the frame and spins it. The opposing player or team calls which side will land face up.
             Scoring. Tennis is scored in terms of points, games, and sets. A player or doubles team scores a point when the opposing side fails to return the ball properly or commits an error. To win a game, one side must score four poi...