World Football On The Net

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—or free kicks such as kickoffs. 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.

Object of the game

The object of the game is to score points by advancing the ball to the opponent's end zone for a six-point touchdown, by kicking the ball through the goal posts for a three-point field goal, or by tackling an opposing ball carrier in their own end zone for a two-point safety. After scoring a touchdown a team may attempt a one-point "extra point," a close-range field-goal-type kick, or a "two-point conversion" in which the ball is advanced into the end zone on a single play instead of a kicked extra-point attempt. The team with the most points when time has expired wins.

Time of play

Collegiate and professional football games are 60 minutes long, divided into four quarters of 15 minutes each. In high school football, 12 minute quarters are usually played. The clock is stopped frequently, however, so that a typical college or professional game can exceed three hours in duration. Timing is stopped after any incomplete pass or any play that ends out of bounds (although in the NFL the clock restarts on the referee's ready-for-play signal outside the last two minutes of the first half and the last five minutes of the second half). In addition, each team is allowed 3 timeouts each half that they may use at their discretion.

The clock may also be stopped for an officials' time-out, after which, if the clock was running, it is restarted. For example; if there is a question as to whether or not a team has moved the ball far enough for a first down, the officials may bring the chains in to measure. While this measurement is taking place, the officials will signal for a stoppage of the clock. Once the measurement is finished and the ball is spotted, the referee will then signal for the clock to restart. Additional situations where officials may take a time-out are to administer a penalty and for an injured player to be removed from the field.

In addition to the game clock, a separate play clock is also used. This counts down the time the offense has to start the next play before it is assessed a penalty for delay of game (see below). This clock is typically 25 seconds from when the referee marks the ball ready for play. The NFL and NCAA use a 40-second play clock that starts immediately after the previous play ends, though for certain delays, such as penalty enforcement, the offense has 25 seconds from when the ball is marked ready.

Officials call for media time-outs (that is, a time-out to allow time for television and radio advertising) after a change of possession (turnover by interception, fumble, or on downs), following a successful PAT (Point(s) After Touchdown), a field goal try, or in the NFL after a kickoff when the opposing team scored, usually when there is more than 5 minutes to play in each quarter. If an instant replay challenge is called during the game, the referees also signal for a media time out. The referee signals these media time-outs by first using the time out signal, then extending both arms in a horizontal position.

Separating the second and third quarters is halftime. Teams change ends of the field at the end of the first quarter and the end of the third quarter. In the NFL, an automatic timeout is called by the officials when there are two minutes left in both the second and the fourth quarters; this is most commonly referred to as the two-minute warning. No such warning is normally given in amateur football, though if there is no visible stadium clock, the referee will give a two-minute warning (four minutes in high school).