Online Help - American Football
Source - Encyclopedia Of Britanica
The American game is played by two teams of 11 players each on a field that measures 100 by 531/3 yd (91.4 by 48.8 m). At each end of the field is an end zone 10 yd (9.14 m) deep, in which stand H- or Y-shaped goal posts.
Play is directed toward gaining possession of the football and moving it (by running or passing) across the opponents goal line, thereby scoring a touchdown, worth six points. Points are also scored by kicking the ball over the crossbar between the goal posts (a field goal, worth three points); downing a player with the ball behind the players own goal line (a safety, worth two points); and a conversion following a touchdown. The conversion is made by kicking the ball over the goal posts (one point) or by a pass or run across the goal line (two points).
The offensive team, led by the quarterback, must gain 10 yd in four tries (downs) or yield possession of the ball. The defending team tries to stop the ball carrier from advancing by tackling. Blocking and tackling make football one of the most rugged of sports, and players wear heavy protective gear.
The first intercollegiate football match in America (more like a 50-person soccer game) was played (1869) between Princeton and Rutgers at New Brunswick, N.J. Harvard began to play a rugby-type game in the 1870s, and within the next decade the distinctive American version evolved. A professional football association was formed in 1920 and renamed the National Football League (NFL) in 1922. Buoyed by the tremendous popularity of professional football after World War II, the NFL absorbed two rival leagues (1949 and 1966) and grew to 28 teams in two conferences by the early 1980s. The league expanded to 30 teams in 1995 and again to 31 teams in 1999.
The annual Super Bowl game for the league championship has been a major sports spectacle since its introduction in 1967. The World League of American Football was a short-lived NFL affiliate that played (1991-92) during the NFLs off-season. It had ten teams, including three in Europe and one in Canada. It was replaced with a six-team all-European league (NFL Europe) in 1995.