American Football is a professional sport played predominantly in North America. A team can score a 6-point touchdown by carrying the football into the opposing team's end zone. This can be done by running the ball past the end line (a running play), or passing the ball to a teammate inside the end zone (a passing play). After a touchdown, a team has the choice of kicking the ball through the goalposts for one point, or carrying the ball back into the end zone again for two points. A 3-point field goal can also be scored by kicking the ball between the goalposts in the opposing team's end zone. Finally, a 2-point safety can be scored by the defensive team if it stops the offensive team with the ball in its own end zone, if the offensive team fumbles in the end zone, if the quarterback intentionally grounds the ball in the end zone, if a blocked kick goes out of the end zone, or if a ball hits the goalpost such as on a bad snap.
In the United States, "football" refers to American Football. Outside the United States, "football" refers to soccer.
As with all popular sports, football has a well-codified set of rules. These are mostly to promote safe gameplay, prevent serious injuries, and keep the game fair.
American football is played on a field that is 120 yards long and 160 feet wide. The last 10 yards of each end of the field are known as end zones. The longer (120 yd) boundary lines are known as "sidelines", while the shorter (100 yd) boundary lines are known as "end lines". Two sets of hash marks run horizontally down the field, and every play starts with the ball on or between the hash marks. A player must carry the ball into (or catch a ball while within) the end zone in order to score a touchdown, worth 6 points.
At the back of each end zone are two vertical "goal posts", standing 18.5 feet apart. These are connected by a crossbar approx. 10 feet from the ground. After a touchdown, the scoring team may attempt a Point After Touchdown (extra point), where a player attempts to kick the ball through the posts. If successful, the team gains an extra point. Additionally, a team may attempt a field goal at any time (usually on a 4th down), though this is rarely attempted if the distance from the goal posts is more than ~35 yards. If successful, this kick is worth three points, though the other team gets possession of the ball regardless of the outcome of the kick.
Each team may have exactly 11 players on the field at any given time, meaning a total of 22 players will be present on the football field during a play. Players are required to wear certain grades of helmets, shoulder pads, thigh/hip pads, and knee pads while playing on the field.
Advancing the Ball
The team with possession of the ball (the offense) is given four attempts (called downs) to advance the ball 10 yards down the field. If the ball is moved at least ten yards during these four attempts, the offense is given a first down, meaning that they have another four chances to move the ball 10 yards (the downs are cumulative; for example, if the offense moves the ball three yards on the first down and five yards on the second down, they only have to move it two yards over the next two downs to gain a first down) If the offense fails to move at least 10 yards over four plays, the opposing team is given possession of the ball.
The yard line on the field where the ball is located is known as the line of scrimmage. The offensive players must line up on the line of scrimmage facing the opponents end zone, while the defense must be behind the line of scrimmage with their backs to their own end zone.
Every play begins with the teams facing each other on the line of scrimmage, and the players may move once the ball is snapped (removed from the ground) by the center. The center usually snaps the ball between his legs to the quarterback (QB), who may take one of several courses of action;
- The quarterback may hand the ball off to a rusher (usually a fullback, halfback, or runningback), who will attempt to run the ball down the field as far as they can before being stopped by the defense.
- The quarterback may opt to throw the ball to a receiver (usually a wide receiver or tight end) who is already several yards down the field. Once the receiver catches the ball, he may continue to run until brought down by a defensive player. If the receiver does not catch the ball, it is called an incomplete pass.
- The quarterback may spike the ball at the ground to stop the game clock, at the expense of a loss of a down.
- The quarterback may run the ball down the field himself; this option is usually unwise, as an injury to the QB can be destructive to an entire team for the whole season.
- The quarterback may kneel on one knee ("genuflect") in order to spend a down while allowing the clock to continue to run. This is the opposite of a spike.
The play ends when the referee's whistle is blown. The whistle can be blown for several reasons;
- The ball carrier is tackled (his knee touches the ground) by members of the opposing team. The location of the ball when the carrier touches the ground is used to determine the amount of yards gained by the offense.
- A forward pass hits the ground or flies out of bounds before being touched. This is an incomplete pass.
- The ball carrier steps out of bounds.
- The offense carries the ball into the endzone, or kicks a field goal.
There are three ways to score in football;
- A touchdown is scored when an offensive player runs the ball into or catches a pass in his opponent's end zone. Unlike Rugby, the ball does not need to be grounded to count as a touchdown ("try" in Rugby).
- After the touchdown, the scoring team may attempt a conversion. The football is placed on the opposing teams 2-yard line, and the offense may either kick it between to goalposts (for an extra point or Point After Touchdown (PAT)), or attempt to run or pass the ball into the endzone (a two-point conversion).
- A Field Goal (FG) occurs when the offense kicks the football between the opposing teams goalposts. A successful field goal is worth three points. A field goal differs from a PAT in that the field goal may be attempted at any time when the offense has possession of the ball (though almost always on a fourth down), and that it is worth three points rather than one.
- A Safety occurs when a defensive player downs a ball carrier in the ball carriers own end zone. A safety is also awarded if the offense fumbles the ball out-of-bounds in their own end zone or have a punt blocked in their own end zone.
Because real American football involves potentially dangerous physical contact, primary-grade schoolkids across the country often play flag football (where pulling a flag off of the opponent represents a tackle) and touch football (where touching the opponent with both hands represents a tackle). Both of these variants usually omit the offensive and defensive lines, and impose a time limit - often 3 seconds - before linebackers can rush the QB.