American football, known in the United States simply as football and sometimes as gridiron outside the United States and Canada, is a sport played between two teams of eleven. The objective of the game is to score points by advancing theball (actually a prolate spheroid) into the opposing team's end zone. The ball canbe advanced by running with it or throwing it to a teammate. Points can be scored bycarrying the ball over the opponent's goal line, catching a pass thrown over that goal line, kicking the ball through the opponent's goal posts or tackling an opposing ball carrier in his own end zone.
In the United States, the major forms are high school football, college football andprofessional football, whichare played under slightly different rules. High school football is governed by the National Federation of State High School Associations, while college football by the National Collegiate Athletic Association and National Association of Intercollegiate Athletics. The major league for professional football is the National Football League (NFL). Other minor professional leagues also exist in theU.S., and may also have slightly different rules from those of the NFL.
The sport is also played in Europe, Japan, Mexico, and other several countries. The International Federation of American Football acts as an international governing body for the sport, but the organization has little standing in the United States.
American football is closely related to Canadian football butwith some differences in rules and the field. Both sports can be traced to early versions of association football and rugby football.
The history of American football can be traced to early versions of rugby football and association football. Both games have their origins in varieties of football played in the United Kingdom in the mid-19thcentury, in which a ball is kicked at a goal and/or run over a line. Many games known as "football" were being played at colleges and universities in the United States in the first half of the 19th century.
American football resulted from several major divergences from rugby football, most notably the rule changes instituted by Walter Camp, considered the "Father of American Football".Among these important changes were the introduction of the line of scrimmageand of down-and-distance rules. In the late 19th and early 20th centuries, game play developments by college coaches such as Eddie Cochems, Amos Alonzo Stagg, Knute Rockne, and Glenn "Pop" Warner helped take advantage of the newly introduced forward pass.
The popularity of collegiate football grew as it became the dominantversion of the sport for the first half of the twentieth century. Bowl games, a college football tradition, attracted a national audience for collegiate teams. Bolstered by fierce rivalries, college football still holds widespread appeal in the US.
Field and players
American football is played on a field 360 by 160 feet (120.0 by 53.3 yards; 109.7 by 48.8 meters). The longerboundary lines are sidelines, while the shorter boundary lines are end lines. Sidelines and end lines are out of bounds. Near each end of the field is a goal line; they are 100 yards (91.4 m) apart. A scoring area called an end zone extends 10 yards (9.1 m) beyond each goal line to each end line. The end zone includes the goal line but not the end line. While the playing field is effectively flat, itis common for a field to be built with a slight crown—with the middle of the field higher than the sides—to allow water to drain from the field.
Yard lines cross the field every 5 yards (4.6 m), and are numbered every 10 yards from each goal line to the 50-yard line, or midfield (similar to a typical rugby league field). Two rows of short lines, known as inbounds lines or hash marks, run at...