Gridiron football
Football is played at professional, collegiate, high school, semi-professional, and amateur levels.
Early on, American and Canadian football developed alongside (but independently from) each other; the root of the game known as "football" today originates with an 1874 game between Harvard and McGill Universities, following which the American school adopted the Canadian school's more rugby-like rules.
[3] Over time, Canadian teams adopted features of the American variant of the game and vice versa.
Both varieties are distinguished from other football sports by their use of hard plastic helmets and shoulder pads, the forward pass, the system of downs, a number of unique rules and positions, measurement in customary units of yards (even in Canada, which largely metricated in the 1970s), and a distinctive brown leather ball in the shape of a prolate spheroid with pointed ends.
Early games had a variety of local rules and were generally similar to modern rugby union and soccer.
[3] Later in the 1860s, teams from universities were playing each other, leading to more standardized rules and the creation of college football.
[3] American football teams and organizations subsequently adopted new rules which distinguished the game from rugby.
[14] Many of these early innovations were the work of Walter Camp, including the sport's line of scrimmage and the system of downs.
[16] Canadian football remained akin to rugby for decades, though a progressive faction of players, chiefly based in the western provinces, demanded changes to the game based on the innovations in American football.
Over the years, the sport adopted more Americanized rules, though it retained some of its historical features, including a 110-yard (100 m) field, 12-player teams, and three downs instead of four.
Each team lines up on opposite halves of the field, with a minimum ten yards of space between them for the kickoff.
The play stops when a player with the ball touches any part of their body other than hand or foot to the ground, runs out of the boundaries of the field, is obstructed from making further forward progress, or a forward pass hits the ground without being caught (in the last case, the ball returns to the spot it was snapped).
Any player on defense can, at any time, attempt to intercept a forward pass in flight, at which point the team gains possession; they can also gain possession by recovering a fumble or stripping the ball away from the ball carrier (a "forced fumble").
A team on offense cannot score points as the direct result of a penalty; a defensive foul committed in the team's own end zone, if the penalty is assessed from the spot of the foul, places the ball at the one-yard line.
In all other circumstances (except for the open-ended and extremely rare unfair act clause), a penalty cannot exceed more than half the distance to the end zone.
In Canada, any kick that goes into the end zone and is not returned, whether it be a punt or a missed field goal, is awarded one single point.
If a team is in its own end zone and commits a foul, is tackled with the ball, or bats, fumbles, kicks or throws the ball backward out of the field of play through the same end zone, the defense scores a safety, worth two points.
Because of the halftime, quarter breaks, time-outs, the minute warnings (two minutes before the end of a half in the NFL, three minutes in Canadian football), and frequent stoppages of the game clock (the clock stops, for example, after every incomplete pass and any time a ball goes out of bounds), the actual time it takes for a football game to be completed is typically over three hours in the NFL[23] and slightly under three hours in the CFL.
