American football Advancing the ball and downs

There are two main ways that the offense can advance the ball: running and passing. In a typical play, the quarterback calls the play, and the center passes the ball backwards and under his legs to the quarterback in a process known as the snap. The quarterback then either hands the ball off to a back, throws the ball or runs with it himself. The play ends when the player with the ball is tackled or goes out of bounds, or a pass hits the ground without a player having caught it. A forward pass can only be legally attempted if the passer is behind the line of scrimmage. In the NFL, a down also ends if the runner's helmet comes off.

The offense is given a series of four plays, known as downs. If the offense advances ten or more yards in the four downs, they are awarded a new set of four downs. If they fail to advance ten yards, possession of the football is turned over to the defense. In most situations, if the offense reaches their fourth down they will punt the ball to the other team, which forces them to begin their drive from further down the field; if they are in field goal range, they might also attempt to score a field goal. A group of officials, the chain crew, keeps track of both the downs and the distance measurements. On television, a yellow line is electronically superimposed on the field to show the first down line to the viewing audience.

SPORTS

American Football

Game play in American football consists of a series of downs, individual plays of short duration, outside of which the ball is dead or not in play. These can be plays from scrimmage – passes, runs, punts, or field goal attempts (from either a place kick or a drop kick) – or free kicks such as kickoffs and fair catch kicks. Substitutions can be made between downs, which allows for a great deal of specialization as coaches choose the players best suited for each particular situation. During a play, each team should have no more than 11 players on the field, and each of them has specific tasks assigned for that specific play.