general rules

Question
Hi David, thanks so much for your time!

I don't know if this is in your expertise, but I would like to know if you can give me the basic guidelines and vocab of football. It's all my friends ever talk about these days and I have no clue WHAT they're talking about. How many points are gained when a specific event happens? What're the names of things that can happen during a play? I just need to know all about football! Thanks!

Answer

This ball is also called a football. The sport is played on a grass field, about 120 yards long and about 53 yards wide. The players wear protective equipment, including a helmet with facemask, shoulder pads, thigh pads, and often a mouth guard. At both ends of the field there are endzones. Each team with 11 players on a side, has four chances to advance the ball 10 yards. If they can advance the ball 10 or more yards until stopped by the opposing team. Teams can score by advancing the ball by either certain players carrying it or throwing it and advance it to the other teams endzone, or kicking it through a goalpost. American football is carefully regulated by time, and rules, enforced by officials, who also determine when a team scores. The main leagues that play Amerian Football are the National Football League, and the National College Athletic Association Football.

SCORES:
TD - 6 points (2 point TD if run back by defense on PAT)
Field goal - 3 points
Safety 2 points (1 point if on a PAT)
PAT or Point after TD - 1 point if kicked or 2 points if run/passed in  


The object of American football is to score more points than the opposing team within the time limit.

Field and players

The numbers on the field indicate the number of yards to the nearest end zone.American football is played on a field 360 feet (120 yards/109.7 m) long by 160 feet (53.3 yards/48.8 m) wide. The longer boundary lines are sidelines, while the shorter boundary lines are end lines. Near each end of the field is a goal line; they are 100 yards (91.4 m) apart. A scoring area called an end zone extends 10 yards (9.1 m) beyond each goal line to each end line.

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 lines, known as inbounds lines or hash marks, parallel the sidelines near the middle of the field. All plays start with the ball on or between the hash marks.

At the back of each end zone are two goalposts (also called uprights) that are 18.5 feet (5.6 m) apart (24 feet (7.3 m) in high school). The posts are connected by a crossbar 10 feet (305 cm) from the ground.

Each team has 11 players on the field at a time. However, teams may substitute for any or all of their players, if time allows, during the break between plays. As a result, players have very specialized roles, and, sometimes (although rarely) almost all of the (at least) 46 active players on an NFL team will play in any given game. Thus, teams are divided into three separate units: the offense, the defense and the special teams.


Start of halves
Similar to association football, the game begins with a coin toss to determine who will kick off to begin the games and which goal each team will defend. The options will be 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 will conduct 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 to either receive the opening kickoff or to kick off
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 (except in the NFL)[8]
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.[9]

Game duration
A standard football game consists of four 15-minute (typically 12 minutes in high-school football) quarters, with a half-time intermission after the second quarter. The clock stops 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 an 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. 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

A line of scrimmage.
A quarterback searching for opportunity to throw a pass.
A running back being tackled when he tries to run with 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, to advance the ball 10 yards (9.1 m) towards their opponent's (the defense's) end zone. When the offense gains 10 yards, it gets a first down, which means the team has another set of four downs to gain yet another 10 yards or score with. If the offense fails to gain a first down (10 yards) after 4 downs, the other team gets possession of the ball at the spot of the football, beginning with their first down.

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 between his legs to a teammate, usually the quarterback.

Players can then advance the ball in two ways:

By running with the ball, also known as rushing. One ball-carrier can hand the ball to another player or throw backwards to another player. These are known as a handoff and a backward pass (sometimes referred to as a lateral) respectively.
By throwing the ball to a teammate, known as a forward pass or as passing the football. 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. The ball can be thrown, pitched, handed-off, or tossed sideways or backwards 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 (tackled) 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 offense maintains possession of the ball unless one of the following things occurs:

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 (it is possible to be downed behind the current line of scrimmage, "losing yardage"). 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, but is not credited as a defensive "turnover" in official statistics. Instead, it goes against the offense's 4th down efficiency percentage.
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 (though see quick kick), 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 posts 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 or forced out of bounds. Backward passes that are not caught do not cause the down to end like 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 and the ball remains in the field of play, a defensive player may also catch the ball and attempt to advance it.
In his own end zone, an offensive ballcarrier is tackled, forced out of bounds or loses the ball out of bounds, or the offense commits certain penalties. This fairly rare occurrence is called a safety.
An offensive ballcarrier fumbles the ball forward into the 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 kicker attempts an extra point.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 with the major difference being that a try requires the player to place the ball on the ground.
After a touchdown, the scoring team attempts a conversion (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 over the crossbar and through the goal posts in the manner of a field goal for 1 point (an extra point or point-after touchdown (PAT)[10]), 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 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 over the crossbar and through the goal posts (uprights). 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 the last 60 years). A field goal is usually attempted on fourth down instead of a punt when the ball is close to the opponent's goal line, or, when there is little or no time left to otherwise score.
A safety, worth 2 points, is scored by the defense when a ball-carrier is tackled in his own end zone. Safeties are also awarded if the offense fumbles the ball out-of-bounds in the end zone, has a kick blocked out of the end zone or commits certain penalties in the end zone. Safeties are relatively rare.

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. A kickoff that goes out-of-bounds anywhere other than the end zone before being touched by the receiving team is considered an illegal procedure penalty, and the ball will be placed where it went out of bounds or 30 yards (27 m) from the kickoff spot, depending on which is more advantageous to the opposite team. Unlike with punts, once a kickoff goes 10 yards, 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. Punts and turnovers in the end zone can also end in a touchback.

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
For a complete list of penalties, see American football rules
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, an official throws a yellow 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.

A few of the most-common fouls include:

False start: An offensive player illegally moves after lining up for--but prior to--the snap. Since the ball is dead, the down is not allowed to begin.
Offside: A defensive or offensive player is on the wrong side of the ball when the ball is snapped. This foul occurs simultaneously with the snap.
Holding: Illegally grasping or pulling an opponent other than the runner.
Pass interference: Illegally contacting an opponent to prevent him from catching a forward pass.
Delay of game: Failing to begin a new play after a certain time from the end of the last one.
Face mask: Grasping the face mask of another player while attempting to block or tackle him.
Illegal block in the back: A blocker contacting a member of the opposing team (who is not the runner) in the back and above the waist.
Clipping: A blocker contacting an opponent (who is not the runner) from behind and at or below the waist.
Under certain circumstances clipping and blocking in the back are legal.

Variations
Variations on these basic rules exist, particularly touch and flag football, which are designed as non-contact or limited-contact alternatives to the relative violence of regular American football. In touch and flag football, tackling is not permitted. Offensive players are "tackled" when a defender tags them or removes a flag from their body, respectively. Both of these varieties are played mainly in informal settings such as intramural or youth games. Another variation is "wrap", where a player is "tackled" when another player wraps his arms around the ball carrier. Professional, intercollegiate, and varsity-level high school football invariably use the standard tackling rules.

Another variation is with the number of players on the field. In sparsely populated areas, it is not uncommon to find high school football teams playing nine-man football, eight-man football or six-man football. Players often play on offense as well as defense. The Arena Football League is a league that plays eight-man football, but also plays indoors and on a much smaller playing surface.


Players
Main article: American football positions
See also: Formation (American football)

This diagram shows typical offensive and defensive formations. The offense (blue) consists of the quarterback (QB), fullback (FB), tailback (TB), wide receivers (WR), tight end (TE), and offensive linemen (C, OG, OT). The defense (red) consists of the defensive line (DL, DE), linebackers (LBs), cornerbacks (CB), strong safety (SS) and free safety (FS). Because teams can change any or all of the players between plays, the number of players at certain positions may differ on a given play. Here the offense is in the Normal I-Formation while the defense is in a 4-3 Normal.Most football players have highly specialized roles. At the college and NFL levels, most play only offense or only defense.


Offense
The offensive line (OL) consists of five players whose job is to protect the passer and clear the way for runners by blocking members of the defense. The lineman in the middle is the Center. Outside the Center are the Guards, and outside them are the Tackles. Except for the center, who snaps the ball to one of the backs, offensive linemen generally do not handle the ball.
The quarterback (QB) receives the snap from the center on most plays. He then hands or tosses it to a running back, throws it to a receiver or runs with it himself. The quarterback is the leader of the offense and calls the plays that are signaled to him from the sidelines.
Running backs (RB) line up behind or beside the QB and specialize in running with the ball. They also block, catch passes and, on rare occasions, pass the ball to others or even receive the snap. If a team has two running backs in the game, usually one will be a halfback (HB) or tailback (TB), who is more likely to run with the ball, and the other will usually be a fullback (FB), who is more likely to block.
Wide receivers (WR) line up near the sidelines. They specialize in catching passes, though they also block for running plays or downfield after another receiver makes a catch.
Tight ends (TE) line up outside the offensive line. They can either play like wide receivers (catch passes) or like offensive linemen (protect the QB or create spaces for runners). Sometimes an offensive lineman takes the tight end position and is referred to as a tackle eligible.[11]
At least seven players must line up on the line of scrimmage on every offensive play. The other players may line up anywhere behind the line. The exact number of running backs, wide receivers and tight ends may differ on any given play. For example, if the team needs only 1 yard, it may use three tight ends, two running backs and no wide receivers. On the other hand, if it needs 20 yards, it may replace all of its running backs and tight ends with wide receivers.


Defense
In contrast to members of the offense, the rules of professional football (NFL Rulebook) and American college football NCAA Rulebook) do not specify starting position, movement, or coverage zones for members of the defensive team, except that they must be in the defensive zone at the start of play. The positions, movements and responsibilities of all defensive players are assigned by the team by selection of certain coverages, or patterns of placement and assignment of responsibilities. The positional roles are customary. These roles have varied over the history of American football. The following are customary defensive positions used in many coverages in modern American football.

The defensive line consists of three to six players who line up immediately across from the offensive line. They try to occupy the offensive linemen in order to free up the linebackers, wreck the backfield of the offense, and tackle the running back if he has the ball before he can gain yardage or the quarterback before he can throw or pass the ball. They are the first line of defense.
Behind the defensive line are the linebackers. They line up between the defensive line and defensive backs and may either rush the quarterback or cover potential receivers. Their main job is to cover the run up the middle.
The last line of defense is known as the secondary, comprising at least three players who line up as defensive backs, which are either cornerbacks or safeties. They cover the receivers and try to stop pass completions. They occasionally rush the quarterback. However, this leaves the field wide open for passing.

Special teams
The units of players who handle kicking plays are known as special teams. Three important special-teams players are the punter, who handles punts, the placekicker or kicker, who kicks off and attempts field goals and extra points, and the long snapper, who snaps the ball for extra points, field goals, and punts. Also included on special teams are the returners. These players return punts or kickoffs and try to get in good field position. These players can also score touchdowns.


Uniform numbering
In the NFL, ranges of uniform numbers are (usually) reserved for certain positions:

1?: Quarterbacks, kickers, and punters
10?9: Quarterbacks, kickers, punters, and wide receivers
20?9: Running backs and defensive backs
50?9: Centers and linebackers
60?9: Offensive and defensive linemen
80?9: Wide receivers and tight ends
90?9: Defensive linemen and linebackers
NCAA and high school rules specify only that offensive linemen must have numbers in the 50-79 range, but the NCAA "strongly recommends" that quarterbacks and running backs have numbers below 50 and wide receivers numbers above 79. This helps officials as it means that numbers 50 to 79 are ineligible receivers, or players that may never receive a forward pass. There are no numbering restrictions on defensive players in the NCAA, other than that no two players with the same jersey number can be on the field at the same time.


Basic strategy
Main article: American football strategy
Because the game stops after every down, giving teams a chance to call a new play, strategy plays a major role in football. Each team has a playbook of dozens to hundreds of plays. Ideally, each play is a scripted, strategically sound team-coordinated endeavor. Some plays are very safe; they are likely to get only a few yards. Other plays have the potential for long gains but at a greater risk of a loss of yardage or a turnover.

Generally speaking, rushing plays are less risky than passing plays. However, there are relatively safe passing plays and risky running plays. To deceive the other team, some passing plays are designed to resemble running plays and vice versa. These are referred to as play-action passes and draws. There are many trick or gadget plays, such as when a team lines up as if it intends to punt and then tries to run or pass for a first down. Such high-risk plays are a great thrill to the fans when they work. However, they can spell disaster if the opposing team realizes the deception and acts accordingly.

The defense also plans plays in response to expectations of what the offense will do. For example, a "blitz" (using linebackers or defensive backs to charge the quarterback) is often attempted when the team on defense expects a pass. A blitz makes downfield passing more difficult but exposes the defense to big gains if the offensive line stems the rush.

Many hours of preparation and strategizing, including film review by both players and coaches, go into the days between football games. This, along with the demanding physicality of football (see below), is why teams typically play at most one game per week.


Physicality
Main article: Health issues in American football

A halfback leads fellow backs through an agility drill at the Air Force AcademyAmerican football is a collision sport. To stop the offense from advancing the ball, the defense must tackle the player with the ball by knocking or pulling him down. As such, defensive players must use some form of physical contact to bring the ball-carrier to the ground, within certain rules and guidelines. Tacklers cannot kick or punch the runner. They also cannot grab the face mask of the runner's helmet or lead into a tackle with their own helmet. Despite these and other rules regarding unnecessary roughness, most other forms of tackling are legal. Blockers and defenders trying to evade them also have wide leeway in trying to force their opponents out of the way. Quarterbacks are regularly hit by defenders coming on full speed from outside the quarterback's field of vision. This is commonly known as a blindside.

To compensate for this, players must wear special protective equipment, such as a padded plastic helmet, shoulder pads, hip pads and knee pads. These protective pads were introduced decades ago and have improved ever since to help minimize lasting injury to players. An unintended consequence of all the safety equipment has resulted in increasing levels of violence in the game. Players may now hurl themselves at one another at high speeds without a significant chance of injury. The injuries that do result tend to be severe and often season or career-ending and sometimes fatal. In previous years with less padding, tackling more closely resembled tackles in Rugby football. Better helmets have allowed players to use their helmets as weapons. This form of tackling is particularily unwise, due to the great potential for brain or spinal injury. All this has caused the various leagues, especially the NFL, to implement a complicated series of penalties for various types of contact. Most recently, virtually any contact with the helmet of a defensive player on the quarterback, or any contact to the quarterback's head, is now a foul.

Despite protective equipment and rule changes to emphasize safety, injuries remain very common in football. It is increasingly rare, for example, for NFL quarterbacks or running backs (who take the most direct hits) to make it through an entire season without missing some time to injury. Additionally, 28 football players, mostly high schoolers, died from direct football injuries in the years 2000-05 and an additional 68 died indirectly from dehydration or other examples of "non-physical" dangers, according to the National Center for Catastrophic Sport Injury Research.[12] Concussions are common, with about 41,000 suffered every year among high school players according to the Brain Injury Association of Arizona.[13]

Extra and optional equipment such as neck rolls, spider pads, rib protectors, and elbow pads help against injury as well, though they do not tend to be used by the majority of players due to their lack of requirement.

The danger of football and the equipment required to reduce it make regulation football impractical for casual play. Flag football and touch football are less violent variants of the game popular among recreational players.

Notes
1^ In North America, the term "football" may refer to either American football or to the similar sport of Canadian football, the meaning usually being clear from the context. This article describes the American variant.
2^ Technically, the ball is a prolate spheroid. See 2006 NCAA Football Rules and Interpretations, Sec. 1, Art. 1
3^ "gridiron." The American Heritage?Dictionary of the English Language, Fourth Edition. Houghton Mifflin Company, 2004. 01 Oct. 2007. [1].
4^ Camp and His Followers: American Football 1876?889. The Journey to Camp: The Origins of American Football to 1889. Professional Football Researchers Association. Retrieved on 2007-05-16.
5^ The History of Football. The History of Sports. Saperecom (2007). Retrieved on 2007-05-15.
6^ NFL History 1869?910. NFL.com. NFL Enterprises LLC (2007). Retrieved on 2007-05-15.
7^ NFL:America's Choice (PDF). National Football League (2007). Retrieved on 2007-08-15.
8^ Coin Toss. NFL Rules Digest. NFL Enterprises LLC (2007). Retrieved on 2008-01-09.
9^ 2005 Rules and Interpretations. National Collegiate Athletic Association (2005). Retrieved on 2008-01-09.
10^ (1 October 2007) 2007 Official Rules of the NFL. Triumph Books. ISBN 1699780288.  
11^ Member - Pro Football Hall of Fame
12^ Annual Survey of Football Injury Research 1931 - 2005, National Center for Catastrophic Sport Injury Research. Updated January 18, 2006. Accessed October 31, 2006
13 Studies Suggest 10% of Arizona High School Football Players Will Suffer a Concussion During This Coming Season PR Newswire press release from the Brain Injury Association of Arizona, August 23, 2005. Accessed October 31, 2006


Go to the following site for information and diagrams:  http://en.wikipedia.org/wiki/American_football

Best of luck
Victor Winnek
NCAA Football official