15 Dimensions are established by the ITF. The reason for numbering scores 15 , 30 , and 40 is unknown. Historical sources suggest the system was originally 15, 30, 45 with the 45 simplified to 40 over time. The best-of-five format is only used in the Grand Slam male tournament matches. baseline: linea di fondo campo bounce: rimbalzo end: met campo interwoven: intrecciato lead: vantaggio odd: dispari shot: tiro sideline: linea laterale di bordo campo winner: vincente (n.) PLAYING TENNIS The equipment The basic equipment required to play tennis is a ball and a racket. A tennis ball should have a diameter between 6.54 and 6.86 centimetres and should weigh between 56 and 59 grams. The racket is about 74 centimetres long and 32 centimetres wide. The strings are usually made of nylon; they are interwoven and make up the hitting surface of the racket, as this is the only part which can hit the ball. A tennis court is nearly 24 metres long; the courts used for singles games are around 8 metres wide, while doubles courts are around 11 metres wide. The service line is 6.4 metres from the net. A baseline in each half and two sidelines mark the boundaries of the court. How the game is played The game starts with one of the players serving the ball; the receiver has to return it successfully. Once a game is completed, it is the turn of the receiver to serve the ball. If the receiver is unable to return the ball from a serve, the server scores an ace and gets the point. Once the serve is returned, the two players engage in a rally, i.e. shots back and forth over the net within the sidelines and baseline. When one of the players fails to hit the ball, the opponent gets a point; in this case the shot is called a winner. A player must wait for the ball to pass the net and come over to their side of the court. Players can hit the ball either before it has bounced or after the first bounce. In a doubles game, the receiving team has to choose the first receiver and then the two players in the team alternate to receive every following shot. The scoring system in tennis Tennis matches are made up of points, games, and sets. A player or team has to score four points to win a game and a minimum of six games, with a two-game difference, to gain a set. To win the match, it is necessary to gain two sets out of three (which is the best-of-three format) or three sets out of five (which is the best-of-five format). The progression of points is the following: First point: 15 Second point: 30 Third point: 40 Fourth point: game. Players are required to change ends after the end of any odd game in a set and after a set is completed. If both players win six games each in a set (6-6), then the set moves to a tie-break, a short game in which the first player who reaches seven points with a two-point lead wins the set.