The American type of football was developed in the 19th century from soccer and rugby（橄榄球）football and it is one of the most popular sports in the world. The beginning of football may have been a game played by the ancient Greeks. In this game, there was no limit（限制）to the number of players.

    The football field of today is 120 yards long and about 53 yards wide. White lines are painted in the field to mark off the distance to the end area. The game is divided into four parts, each fifteen minutes long. The first two parts are known as the first half. There is a rest period （时间）between the two halves. It usually lasts about fifteen minutes.

    Each team has eleven players. Players are required to wear protective equipment（设备）to help keep the body safe during the game. Hard hats are worn to protect the head and the face. Pads（防护垫）are worn to protect the shoulders, arms and legs.

    The football is made of leather and is brown in colour. It is shaped much like an oval（椭圆形）and has white rings near each end of the football. These rings help the players see the ball when it is thrown or someone is running with it.

    The most famous football game of the year is the Super Bowl. It is televised around the world and is watched by millions of people each year.