游戏玩法

Teams advance across the field through the execution of short, distinct plays, which involve the possession of a brown, ovoid ball with ends tapered to a point. The ball has two one-inch-wide stripes.

Kickoff

Play begins with one team place-kicking the ball from its own 35-yard line. Both teams then attempt to catch the ball. The player who recovers the ball may run while holding the ball, or throw the ball to a teammate, so long as the throw is not forward.

Stoppage of play

Play stops when the ball carrier's knee, elbow, or any other body part aside from the feet and hands, is forced to the ground (a tackl'); when a touchdown (see below) or a field goal is scored; when the ball leaves the playing area by any means (being carried, thrown, or fumbled out of bounds); or when the ball carrier is in a standing position but can no longer move. If no score has been made, the next play starts from scrimmag'.

Scrimmage

Before scrimmage, an official places the ball at the spot it became dead, but no nearer than 24 yards from the sideline or 1 yard from the goalline. The line parallel to the end zone passing through the ball is referred to as the line of scrimmage. This line is a sort of "no-man's land": players must stay on their respective sides of this line until the play has begun again. For a scrimmage to be valid the team in possession of the football must have seven players, excluding the quarterback, within one yard of the line of scrimmage. The defending team, however, must stay a yard or more back from the line of scrimmage.

Live play

On the field at the beginning of a play are two teams of 12. The team in possession of the ball is the offence and the team defending is referred to as the defence. Play begins with a backwards pass through the legs by a member of the offensive team, to the quarterback or punter. If the quarterback or punter receives the ball, he may then do any of the following:

• run with the ball, attempting to run farther down field (gaining yardage). The ball-carrier may run in any direction he sees fit (including backwards).
• drop-kic' the ball, dropping it onto the ground and kicking it on the bounce. (This play is exceedingly rare in both Canadian and American football, although in the Canadian game it is sometimes used as a last-second "desperation play" if the team is behind by less than three points.)
• pass the ball laterally or backwards to a teammate. This play is known as a latera', and may come at any time on the play. A pass which has any amount of forward momentum is a forward pas' (see below); forward passes are subject to many restrictions which do not apply to laterals.
• hand-of'--hand the ball off to a teammate, typically a runningback or the fullback.
• pun' the ball; dropping it in the air and kicking it befor' it touches the ground.
• place the ball on the ground for a place kic'
• throw a forward pas', where the ball is thrown to a receiver located farther down field (closer to the opponent's goal) than the thrower is. Forward passes are subject to the following restrictions:
  • They must be made from behin' the line of scrimmage
  • Only one forward pass may be made on a play
  • The pass must be made in the direction of an eligible receiver.

Each play constitutes a dow'. The offence must advance the ball at least ten yards towards the opponents' goal line within three downs or forfeit the ball to their opponents. Once ten yards have been gained the offence gains a new set of three downs. It must be noted that they do not accumulate, so that if one completes 10 yards on their first play, they lose the other two downs, instead of being granted three on top of their remaining two. If a team fails to gain ten yards in two downs they usually punt the ball on third down or try to kick a field goal (see below), depending on their position on the field.