rules for playing american football
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 1-yard (91.4 cm) intervals perpendicular to the sidelines near the middle of the field. All plays start with the ball on or between the hash marks. Because of the arrangement of the lines, the field is occasionally referred to as a gridiron in a reference to the cooking grill with a similar pattern of lines.
At the back of each end zone are two goalposts (also called uprights) connected by a crossbar 10 feet (3.05 m) from the ground. For high skill levels, the posts are 18 feet 6 inches (5.64 m) apart. For lower skill levels, these are widened to 23 feet 4 inches (7.11 m).
Each team has 11 players on the field at a time. Usually there are many more players off the field. There are 45 active players on an NFL team. However, if time allows, teams may substitute for any or all of their players during the breaks between plays. As a result, players have very specialized roles and are divided into three separate units: the offense, the defense and the special teams. Although this is rare, in some games, almost all of the players will play during the course of the game.
Start of halves
Similarly to association football, the game begins with a coin toss to determine which team will kick off to begin the game and which goal each team will defend.The options are presented again to start the second half; the choices for the first half do not automatically determine the start of the second half. The referee conducts the coin toss with the captains (or sometimes coaches) of the opposing teams. The team that wins the coin toss has three options:
They may choose whether to kick or receive the opening kickoff.
They may choose which goal to defend.
They may choose to defer the first choice to the other team and have first choice to start the second half.
Whatever the first team chooses, the second team has the option on the other choice (for example, if the first team elects to receive at the start of the game, the second team can decide which goal to defend).
At the start of the second half, the options to kick, receive, or choose a goal to defend are presented to the captains again. The team which did not choose first to start the first half (or which deferred its privilege to choose first) now gets first choice of options.
A standard football game consists of four 15-minute quarters (12-minute quarters in high-school football and often shorter at lower levels),with a 12-minute half-time intermission after the second quarter.At all levels, a down (play) that begins before time expires is allowed to continue until its completion, even after the clock reaches zero. The clock is also stopped after certain plays, therefore, a game can last considerably longer (often more than three hours in real time), and if a game is broadcast on television, TV timeouts are taken at certain intervals of the game to broadcast commercials outside of game action. If an NFL game is tied after four quarters, the teams play an additional period lasting up to 15 minutes. In a regular season NFL overtime game, the first team that scores wins, even if the other team does not get a possession; this is referred to as sudden death. However, in a post-season NFL game during the playoffs, if the first team with possession scores only a field goal, the other team is allowed the opportunity to match or better this score. This rule only affects playoff games in overtime in which the first team with possession scores a field goal: if the first team with possession scores a touchdown, the sudden death rules take effect. In a regular-season NFL game, if neither team scores in overtime, the game is a tie. In an NFL playoff game, additional overtime periods are played, as needed, to determine a winner. College overtime rules are more complicated and are described in Overtime (sport).
Advancing the ball
Advancing the ball in American football resembles the six-tackle rule and the play-the-ball in rugby league. The team that takes possession of the ball (the offense) has four attempts, called downs, in which to advance the ball at least 10 yards (9.1 m) toward their opponent's (the defense's) end zone. When the offense succeeds in gaining at least 10 yards, it gets a first down, meaning the team starts a new set of four downs to gain yet another 10 yards or to score. If the offense fails to gain a first down (10 yards) after four downs, the other team gets possession of the ball at the point where the fourth down ended, beginning with their first down to advance the ball in the opposite direction.
Except at the beginning of halves and after scores, the ball is always put into play by a snap. Offensive players line up facing defensive players at the line of scrimmage (the position on the field where the play begins). One offensive player, the center, then passes (or "snaps") the ball backwards between his legs to a teammate behind him, usually the quarterback.
Players can then advance the ball in two ways:
By running with the ball, also known as rushing.
By throwing the ball to a teammate, known as a pass or as passing the football. If the pass is thrown down-field, it is known as a forward pass. The forward pass is a key factor distinguishing American and Canadian football from other football sports. The offense can throw the ball forward only once during a down and only from behind the line of scrimmage. However, the ball can be handed-off to another player or thrown, pitched, or tossed sideways or backwards (a lateral pass) at any time.
A down ends, and the ball becomes dead, after any of the following:
The player with the ball is forced to the ground (a tackle) or has his forward progress halted by members of the other team (as determined by an official).
A forward pass flies beyond the dimensions of the field (out of bounds) or touches the ground before it is caught. This is known as an incomplete pass. The ball is returned to the most recent line of scrimmage for the next down.
The ball or the player with the ball goes out of bounds.
A team scores.
Officials blow a whistle to notify players that the down is over.
Before each down, each team chooses a play, or coordinated movements and actions, that the players should follow on a down. Sometimes, downs themselves are referred to as "plays."
Change of possession
The team fails to get a first down— i.e., in four downs they fail to move the ball past a line 10 yards ahead of where they got their last first down. The defensive team takes over the ball at the spot where the 4th-down play ends. A change of possession in this manner is commonly called a turnover on downs.
The offense scores a touchdown or field goal. The team that scored then kicks the ball to the other team in a special play called a kickoff.
The offense punts the ball to the defense. A punt is a kick in which a player drops the ball and kicks it before it hits the ground. Punts are nearly always made on fourth down, when the offensive team does not want to risk giving up the ball to the other team at its current spot on the field (through a failed attempt to make a first down) and feels it is too far from the other team's goal post to attempt a field goal.
A defensive player catches a forward pass. This is called an interception, and the player who makes the interception can run with the ball until he is tackled, forced out of bounds, or scores.
An offensive player drops the ball (a fumble) and a defensive player picks it up. As with interceptions, a player recovering a fumble can run with the ball until tackled, forced out of bounds, or scoring. Passes that are thrown either backwards or parallel with the line of scrimmage (lateral passes) that are not caught do not cause the down to end as incomplete forward passes do; instead the ball is still live as if it had been fumbled. Lost fumbles and interceptions are together known as turnovers.
The offensive team misses a field goal attempt. The defensive team gets the ball at the spot where the previous play began (or, in the NFL, at the spot of the kick). If the unsuccessful kick was attempted from within 20 yards (18.3 m) of the end zone, the other team gets the ball at its own 20 yard line (that is, 20 yards from the end zone). If a field goal is missed or blocked and the ball remains in the field of play, a defensive player may pick up the ball and attempt to advance it.
While in his own end zone, an offensive ball carrier is tackled, forced out of bounds, loses the ball out of bounds, or the offense commits certain fouls in the end zone. This fairly rare occurrence is called a safety.
An offensive ball carrier fumbles the ball forward into the opposing end zone, and then the ball goes out of bounds. This extremely rare occurrence leads to a touchback, with the ball going over to the opposing team at their 20 yard line (Note that touchbacks during non-offensive special teams plays, such as punts and kickoffs, are quite common).
Scoring
A team scores points by the following plays:
A touchdown (TD) is worth 6 points. It is scored when a player runs the ball into or catches a pass in his opponent's end zone.A touchdown is analogous to a try in rugby. Unlike rugby, a player does not have to touch the ball to the ground to score; a touchdown is scored any time a player has possession of the ball while any part of the ball is beyond the vertical plane created by the leading edge of the opponent's goal line stripe (the stripe itself is a part of the end zone).
After a touchdown, the scoring team attempts a try (which is also analogous to the conversion in rugby). The ball is placed at the other team's 3-yard (2.7 m) line (the 2-yard (1.8 m) line in the NFL). The team can attempt to kick it through the goalposts (over the crossbar and between the uprights) in the manner of a field goal for 1 point (an extra point or point-after touchdown (PAT), or run or pass it into the end zone in the manner of a touchdown for 2 points (a two-point conversion). In college football, if the defense intercepts or recovers a fumble during a one or two point conversion attempt and returns it to the opposing end zone, the defensive team is awarded the two points.
A field goal (FG) is worth 3 points, and it is scored by kicking the ball through the goalposts defended by the opposition. Field goals may be placekicked (kicked when the ball is held vertically against the ground by a teammate) or drop-kicked (extremely uncommon in the modern game, with only two successes in sixty-plus years in the NFL). A field goal is usually attempted on fourth down instead of a punt when the ball is close enough to the opponent's goalposts, or, when there is little or no time left to otherwise score.
A safety, worth 2 points, is scored by the opposing team when the team in possession at the end of a down is responsible for the ball becoming dead behind its own goal line. For instance, a safety is scored by the defense if an offensive player is tackled, goes out of bounds, or fumbles the ball out of bounds in his own end zone.Safeties are relatively rare. Note that, though even more rare, the team initially on offense during a down can score a safety if a player of the original defense gains possession of the ball in front of his own goal line and then carries the ball or fumbles it into his own end zone where it becomes dead. However, if the ball becomes dead behind the goal line of the team in possession and its opponent is responsible for the ball being there (for instance, if the defense intercepts a forward pass in its own end zone and the ball becomes dead before the ball is advanced out of the end zone) it is a touchback: no points are scored and the team last in possession keeps possession with a first down at its own 20 yard line. In amateur football, in the extremely rare instance that a safety is scored on a try, it is worth only 1 point.
Kickoffs and free kicks
Each half begins with a kickoff. Teams also kick off after scoring touchdowns and field goals. The ball is kicked using a kicking tee from the team's own 30-yard (27 m) line in the NFL and college football (as of the 2007 season). The other team's kick returner tries to catch the ball and advance it as far as possible. Where he is stopped is the point where the offense will begin its drive, or series of offensive plays. If the kick returner catches the ball in his own end zone, he can either run with the ball, or elect for a touchback by kneeling in the end zone, in which case the receiving team then starts its offensive drive from its own 20 yard line. A touchback also occurs when the kick goes out-of-bounds in the end zone. (Punts and turnovers in the end zone can also result in a touchback). A kickoff that goes out-of-bounds anywhere other than the end zone before being touched by the receiving team is a foul, and the ball will be placed within the hash marks of the yard line where it went out of bounds, or 30 yards (27 m) from the kickoff spot, depending on which is more advantageous to the receiving team.Unlike with punts, once a kickoff goes 10 yards and the ball has hit the ground, it can be recovered by the kicking team.A team, especially one who is losing, can try to take advantage of this by attempting an onside kick.
After safeties, the team that gave up the points must free kick the ball to the other team from its own 20 yard line.
Penalties
A penalty flag on the field during a game on November 16, 2008 between the San Francisco 49ers and St. Louis Rams.
Main article: Penalty (American football)
Fouls (a type of rule violation) are punished with penalties against the offending team. Most penalties result in moving the football towards the offending team's end zone. If the penalty would move the ball more than half the distance towards the offender's end zone, the penalty becomes half the distance to the goal instead of its normal value.
Most penalties result in replaying the down. Some defensive penalties give the offense an automatic first down.Conversely, some offensive penalties result in loss of a down (loss of the right to repeat the down). If a penalty gives the offensive team enough yardage to gain a first down, they get a first down, as usual.
If a foul occurs during a down (after the play has begun), the down is allowed to continue and an official throws a yellow penalty flag near the spot of the foul. When the down ends, the team that did not commit the foul has the option of accepting the penalty, or declining the penalty and accepting the result of the down.
Variations
See also: List of gridiron football codes
Limited contact
touch football. A play ends when a defender touches the ball carrier (sometimes with two hands).
flag football. A play ends when a defender removes a designated token ("flag") worn by the ball carrier.
Wrap. A play ends when a defender wraps his arms round the ball carrier.
Fewer players
nine-man football
eight-man football
six-man football
Smaller field
The Arena Football League is a league that plays eight-man football, but also plays indoors and on a much smaller playing surface with rule changes to encourage a much more offensive game.
Catch and Run
In this game, the children split into two teams and line up at opposite sides of the playing field. One side throws the ball to the other side. If the opposing team catches the ball, that player tries to run to the throwing teams touchdown without being tagged/tackled. If no one catches the ball or if the player is tagged/tackled, then that team has to throw the ball to the opposing team. This repeats until time runs out or the players decide to quit.
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