Larry Fitzgerald catches a pass at the 2009 Pro Bowl
|First played||November 6, 1869, Princeton vs. Rutgers|
|Team members||11 per side
Both teams can substitute players freely between downs
|Categorization||Team sport, ball game|
Pads (shoulder and knee)
|Venue||Football field (or gridiron)|
|Olympic||No; demonstrated at the 1932 Summer Olympics|
American football, known in the United States as football, is a team sport. It is played by two teams, eleven players to a side, who advance an oval ball over a rectangular field that is 120 yards long by 53.3 yards wide and has goalposts at both ends. The team in possession of the ball (the offense) attempts to advance down the field by running with or passing the ball. To continue their drive, the offense must advance the ball at least 10 yards down the field in a series of four downs. If they succeed, they receive a new set of four downs to continue their drive. Otherwise, they lose control of the ball to the opposing team. The offense can score points by advancing the ball into the end zone (a touchdown) or by kicking the ball through the opponent's goalpost (a field goal), while the defense can score points by forcing an offensive turnover and advancing the ball into the offense's end zone or by tackling the ballcarrier in the offense's end zone (a safety). The team that has scored the most points by the end of the game wins.
American football evolved from early forms of rugby, particularly rugby union, and association football (soccer). The first game was played on November 6, 1869 under a set of rules resembling those of rugby and soccer. A set of rule changes instituted from 1880 onward by Walter Camp established the snap, eleven-player teams and downs. Later rule changes legalized the forward pass, created the neutral zone and specified the width of the football.
American football is the most popular sport in the United States today, and the National Football League (NFL) is its most popular league. The league's championship, the Super Bowl, is among the most-watched club sporting events in the world.
American football evolved from the sport of rugby football. The first football game was played on November 6, 1869 between Rutgers and Princeton. The game was played between two teams of 25 players each, used a round ball, and resembled a combination of rugby and soccer in its rules. The ball could not be picked up or carried, but it could be kicked or batted with the feet, hands, head or sides.
Collegiate play continued for several years in which matches were played using the rules of the host school. Representatives of Yale, Columbia, Princeton and Rutgers met on October 19, 1873 to create a standard set of rules. Teams were set at 20 players each, and fields of 400 by 250 feet were specified. Harvard abstained from the conference, as they favored a rugby-style game that allowed running with the ball.
An 1875 Harvard-Yale game played under rugby-style rules was observed by two impressed Princeton athletes. These players introduced the sport to Princeton, a feat the Professional Football Researchers Association compared to "selling refrigerators to Eskimos." Princeton, Harvard, Yale and Columbia then agreed to intercollegiate play using a form of rugby union rules with a modified scoring system. These schools formed the Intercollegiate Football Association, although Yale did not join until 1879. Yale player Walter Camp, now regarded as the "Father of American Football," passed rule changes in 1880 that reduced the team size from 15 to 11 players and instituted the snap to replace the chaotic and inconsistent scrum.
Evolution of the game
The introduction of the snap resulted in unexpected strategy changes. Previously, the strategy had been to punt if a scrum resulted in bad field position. A group of Princeton players realized that, as the snap was uncontested, they now could hold the ball indefinitely to prevent their opponent from scoring. In 1881, both contestants in a Yale-Princeton game used this strategy to maintain their undefeated records. Each team held the ball, gaining no yardage, for an entire half. This "block game" proved extremely unpopular with spectators and fans.
A rule change was necessary to prevent this, and a reversion to the scrum was considered until Camp passed a rule in 1882 that stated that a team would have three downs, or tackles, to advance the ball five yards. Failure to do so would forfeit control of the ball to the other team. This change made American football a separate sport from rugby, and the resulting five-yard lines added to the field made it resemble a gridiron in appearance. Other major rules changes included a reduction of the field size, to 110 yards long by 53.3 yards wide, and the adoption of a scoring system that awarded four points for a touchdown, two for a safety and a goal following a touchdown, and five for a goal from field. The last major remnant of rugby was removed in 1888, when tackling below the waist was legalized.
Football remained a violent sport despite these innovations. Dangerous mass-formations like the flying wedge resulted in serious injuries or even death. A 1905 peak of 19 fatalities nationwide resulted in President Theodore Roosevelt's threat to abolish the game unless major changes were made. Sixty-two schools met in New York City to discuss rule changes on December 28, 1905. These proceedings resulted in the formation of the Intercollegiate Athletic Association of the United States, later named the National Collegiate Athletic Association (NCAA).
The legal forward pass was introduced in 1906 after its suggestion by John Heisman, although its impact was limited due to the restrictions placed on its use. Further 1906 rules changes included the reduction of the time of play from 70 to 60 minutes and the increase of the distance requirement for a first down to 10 yards over three downs. Additionally, the neutral zone was created along the width of the football. Field goals were lowered to three points in 1909 and touchdowns raised to six points in 1912. The field was also reduced to 100 yards long, but two 10-yard-long end zones were created, and teams were given four downs instead of three to advance the ball 10 yards. The roughing-the-passer penalty was implemented in 1914, and eligible players were first allowed to catch the ball anywhere on the field in 1918.
The professional era
The first instance of professional play in football was on November 12, 1892, when William "Pudge" Heffelfinger was paid $500 to play a game for the Allegheny Athletic Association in a match against the Pittsburgh Athletic Club. This is the first recorded instance of an player being paid to participate in a game of American football, although many athletic clubs in the 1880s offered to help players attain employment, gave out trophies or watches that players would pawn for money, or paid double in expense money. Football at the time had a strict sense of amateurism, and direct payment to players was frowned upon, if not outright illegal.
Professional play became common, and with it came rising salaries, unpredictable player movement, and the illegal use of amateur collegiate players in professional games. The National Football League, a group of professional teams that was originally established in 1920 as the American Professional Football Association, aimed to solve these problems. This new league's stated goals included an end to bidding wars over players, prevention of the use of college players, and abolition of the practice of paying players to leave another team. The NFL by 1922 had established itself as the premier professional football league.
The dominant form of football at the time was played at the collegiate level, but the upstart NFL received a boost to its legitimacy in 1925 when an NFL team, the Pottsville Maroons, defeated a team of Notre Dame all-stars in an exhibition game. A greater emphasis on the passing game helped professional football to further distinguish itself from the college game during the late 1930s. Football in general became increasingly popular following the 1958 NFL Championship game, a match between the Baltimore Colts and the New York Giants that is still referred to as the "Greatest Game Ever Played." The game, a 23-17 overtime victory by the Colts, was seen by millions of television viewers and had a major impact on the popularity of the sport. This helped football to become the most popular sport in the United States by the mid-1960s.
A rival, the American Football League (AFL), arose in 1960 and challenged the NFL's dominance. The AFL began in relative obscurity but survived for several years due to a television contract with the ABC network. Competition for players heated up in 1965, when the AFL New York Jets signed rookie Joe Namath to a then-record USD $437,000 contract. A five-year, $40 million dollar NBC television contract followed, which helped to sustain the young league. The bidding war for players ended in 1966, when the two leagues agreed on a merger that would take full effect in 1970. This agreement provided for a common draft that would take place each year, and it instituted an annual championship game to be played between the champions of each league. That game began play in 1966 and came to be known as the Super Bowl.
College football maintained a tradition of postseason bowl games. Each bowl game would be associated with a particular conference, and earning a spot in a bowl game was the reward for winning a conference. This arrangement was profitable, but it tended to prevent the two top-ranked teams from meeting in a true national championship game, as they would normally be committed to the bowl games of their respective conferences. Several systems have been used since 1992 to determine a national champion of college football. The first was the Bowl Coalition, in place from 1992-94. This was replaced in 1995 by the Bowl Alliance, which gave way in 1997 to the Bowl Championship Series (BCS). The BCS arrangement has been controversial, and will be replaced in 2014 by a four-team playoff system.
American football is today the most popular sport in the United States. In a 2013 poll conducted by Harris Interactive, professional and college football were the first and third most popular sports, and 45% of participants ranked some form of the game as their favorite sport. The Super Bowl is the most popular single-day sporting event in the United States and is among the biggest club sporting events in the world.
Teams and positions
A game is played between two teams of 11 players each. It is legal to have fewer players on the field, but playing with more on the field is punishable by a penalty. Teams may substitute any number of their players between downs, and the original system in which all players participate in all plays has been replaced by a "platoon" system that uses specialized offensive, defensive and special teams squads.
Individual players in a football game must be designated with a uniform number between 1 and 99. NFL teams are required to number their players by a league-approved numbering system, and any exceptions must be approved by the Commissioner. NCAA and NFHS teams are "strongly advised" to number their offensive players according to a league-suggested numbering scheme.
The offensive team must line up in a legal formation before they can snap the ball. An offensive formation is considered illegal if there are more than four players in the backfield or fewer than five players numbered 50-79 on the offensive line. Players can temporarily line up in a position whose eligibility is different than their number permits as long as they immediately report the change to the referee, who then informs the defensive team of the change. Neither team's players, with the exception of the snapper, are allowed to line up in or cross the neutral zone until the ball is snapped. Interior offensive linemen are not allowed to move until the snap of the ball.
Backs and backfield
The main backfield positions are the quarterback (QB), halfback/tailback (HB/TB) and fullback (FB). The quarterback is the leader of the offense. Either he or a coach calls the plays. Quarterbacks typically inform the rest of the offense of the play in the huddle before the team lines up. The quarterback lines up behind the center to take the snap and then hands the ball off, throws it or runs with it.
The primary role of the halfback, who is also known as the tailback, is to carry the ball on running plays. Halfbacks may also serve as receivers. Fullbacks tend to be larger than halfbacks and function primarily as blockers, but they are sometimes used as runners in short-yardage situations and often are not used in passing situations.
The offensive line consists of several players whose primary function is blocking. The leader of the offensive line is the center (C), who is responsible for snapping the ball to the quarterback and for making sure that the other linemen do their jobs during the play. On either side of the center are the guards (G), while tackles (T) line up outside of the guards.
The principal receivers are the wide receivers (WR) and the tight ends (TE). Wide receivers line up on or near the line of scrimmage, split outside of the line. The main goal of the wide receiver is to catch passes thrown by the quarterback, but they may also function as decoys or as blockers during running plays. Tight ends line up outside of the tackles and function both as receivers and as blockers.
The defensive line consists of defensive ends (DE) and defensive tackles (DT). Defensive ends line up on the end of the line, while defensive tackles line up on the inside. Their primary responsibilities are to stop running plays on the inside and outside, respectively, as well as to pressure the quarterback on passing plays and to occupy the line so that the linebackers can break through.
Linebackers line up behind the defensive line but in front of the defensive backfield. They are divided into two types: middle linebackers (MLB) and outside linebackers (OLB). Linebackers are the defensive leaders and call the defensive plays. Their diverse roles include defending the run, pressuring the quarterback, and guarding backs, wide receivers and tight ends in the passing game.
The defensive backfield, often called the "secondary," consists of cornerbacks (CB) and safeties (S). Safeties are themselves divided into free safeties (FS) and strong safeties (SS). Cornerbacks line up outside the defensive formation and cover wide receivers, while safeties line up between the cornerbacks but farther back in the secondary. The defensive backfield is responsible for stopping deep passes and running plays.
Special teams unit
Field goals and kickoffs
Three positions are specific to the field goal and PAT (point after touchdown) unit: the placekicker (K or PK), holder (H) and long snapper (LS). The long snapper's job is to snap the ball to the holder, who will catch the ball and position it for the placekicker. On kickoffs, the ball is kicked off of a tee. The player on the receiving team who catches the ball is the "kickoff returner" (KR).
Punts and punt returners
The positions specific to punt plays are the punter (P), long snapper and gunners. The long snapper snaps the ball directly to the punter, who then drops the ball and kicks it. Gunners line up outside of the line and race down the field to tackle the player on the receiving team who catches the ball, known as the "punt returner" (PR).
American football is a violent game, and players wear armor-like padding to protect themselves. At minimum, players wear a protective football helmet, which has a face mask, and a set of shoulder pads. Additional padding may be required, depending on the league. This may include thigh pads and guards, knee pads, chest protectors, and mouth guards. College and high school play require the use of a mouthguard. Despite these protections, injuries do occur - particularly concerning are head injuries such as concussions. Concussions are often caused by helmet-to-helmet or upper-body contact between opposing players, although the helmets have prevented more serious injuries such as skull fractures.
The rules of American football vary somewhat from league to league, but each level of the sport has a prominent, national body that determines a unified code of rules for that level of play. The National Football League (NFL) is the highest level of professional football in the United States. The National Collegiate Athletic Association (NCAA), which manages university athletics in the United States for most colleges and universities, maintains the rules for college football, and high school football is overseen by the National Federation of State High School Associations (NFHS). The largest organization for youth football leagues, whose players are younger than high school age, is the Pop Warner Little Scholars.
There are several ways to score in American football. The touchdown, worth six points, is the most valuable scoring play. A touchdown is scored when the ball is advanced into or caught in, or when a ball in play is recovered in, the end zone of the opposing team. The scoring team then attempts a try, more commonly known as the point(s)-after-touchdown (PAT), which is a single scoring opportunity. A PAT is attempted from the two- or three-yard line, depending on the level of play. If scored by a placekick, it is worth one point and is called the extra point. If it is scored by what would normally be a touchdown, it is called the two-point conversion and is worth two extra points. No extra points are awarded on a failed attempt. The extra point is almost always successful at the professional level and slightly less so at the amateur level, while the two-point conversion has a significantly lower success rate. A field goal, worth three points, is scored when the ball is placekicked or, very rarely, dropkicked through the uprights and over the crossbars of the defense's goalposts. After a PAT attempt or successful field goal the scoring team must kick the ball off to the other team.
Football games are played on a rectangular field that measures 120 yards (109.7 meters) long and 53.3 yards (48.7 meters) wide. Lines marked along the ends and sides of the field are known respectively as the end lines and side lines, and goal lines are marked 10 yards outward from each end line. Weighted pylons are placed on the inside corner of the intersections of the goal lines and end lines.
White markings on the field identify the distance from the end zone. Inbound lines, or hash marks, are short parallel lines that mark off one-yard increments. Yard lines, which run the width of the field, are marked every five yards. A line one yard wide is placed at each end of the field. This line is marked at the center of the two-yard line in professional play and at the three-yard line in college play. Numerals that display the yard lines in multiples of ten are placed along both sides of the field.
Goalposts are at the center of the plane of each of the two end lines. The crossbar of these posts is ten feet above the ground, and the uprights at the ends of the crossbar extend 30 feet (9.1 meters) on professional fields, a minimum of 30 feet on college fields, and a minimum of 10 feet (3.1 meters) on high school fields. Goal posts are padded at the base, and orange ribbons are normally placed at the tip of each upright.
Duration and time stoppages
Football games last for a total of 60 minutes in professional and college play and are divided into two halves of 30 minutes and four quarters of 15 minutes. High school football games are 48 minutes in length with two halves of 24 minutes and four quarters of 12 minutes. The two halves are separated by a halftime period, and the first and third quarters are also followed by a short break. Teams switch goals following the first and third quarters. If a down is in progress when a quarter ends, play continues until the down is completed.
Games last longer than their defined length due to play stoppages, so that the average NFL game lasts just over three hours. Time in a football game is measured by the game clock. An operator is responsible for starting, stopping and operating the game clock based on the direction of the appropriate official. A separate clock, the play clock, is used to determine if a delay of game infraction has been committed. If the play clock expires before the ball has been snapped or free-kicked, a delay of game foul is called on the offense. The play clock is set to 40 seconds in professional and college football and to 25 seconds in high school play or following certain administrative stoppages in the former levels of play.
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.
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 ball is turned over to the defense. Normally, 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. 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.
There are two categories of kicks in football: scrimmage kicks, which can be executed by the offensive team on any down from behind or on the line of scrimmage, and free kicks. The free kicks are the kickoff, which starts the first and third quarters and overtime and follows a try attempt or a successful field goal, and the safety kick, which follows a safety.
On a kickoff, the ball is placed at the 35-yard line of the kicking team in professional and college play and at the 40-yard line in high school play. The ball may be drop-kicked or place-kicked. If a place kick is chosen, the ball can be placed on the ground or on a tee, and a holder may be used in either case. On a safety kick, the kicking team kicks the ball from their own 20-yard line. They can punt, drop-kick or place-kick the ball, but a tee may not be used in professional play. Any member of the receiving team may catch or advance the ball, and the ball may be recovered by the kicking team once it has gone at least ten yards or has been touched by any member of the receiving team.
Place kicks and drop kicks can be used to score points from scrimmage, but the place kick is the standard method used due to the difficulty of reliably dropkicking a football. Once the ball has been kicked from a scrimmage kick, it can be advanced by the kicking team only if it is caught or recovered behind the line of scrimmage. If it is touched or recovered by the kicking team beyond this line, it becomes dead at the spot where it was touched. The kicking team is prohibited from interfering with the receiver's opportunity to catch the ball, and the receiving team has the option of signaling for a fair catch. This prohibits the defense from blocking into or tackling the receiver, but the play ends as soon as the ball is caught and the ball may not be advanced.
Officials and fouls
Officials are responsible for enforcing game rules and monitoring the clock. All officials carry a whistle and wear black-and-white striped shirts and black hats except for the referee, whose hat is white. Each carries a weighted yellow flag that is thrown to the ground to signal that a penalty has been called. An official who spots multiple penalties will throw his hat as a secondary signal. The seven officials on the field are each tasked with a different set of responsibilities:
- The referee is charged with oversight and control of the game and is the authority on the score, the down number, and any and all rule interpretations in discussions between the other officials. He announces all penalties and discusses the infraction with the offending team's captain, monitors for illegal hits against the quarterback, makes requests for first-down measurements, and notifies the head coach whenever a player is ejected.
- The umpire, who is positioned in the backfield, watches play along the line of scrimmage to make sure that no more than 11 offensive players are on the field prior to the snap and that no offensive linemen are illegally downfield on pass plays. He monitors the contact between offensive and defensive linemen and calls most of the holding penalties. The umpire records the number of timeouts taken and the winner of the coin toss and the game score, assists the referee in situations involving possession of the ball close to the line of scrimmage, determines whether player equipment is legal, and dries wet balls prior to the snap if a game is played in rain.
- The head linesman lines up opposite the line judge. He watches for any line-of-scrimmage and illegal use-of-hands violations and assists the line judge with illegal shift or illegal motion calls. The head linesman also rules on out-of-bounds calls that happen on his side of the field, oversees the chain crew and marks the forward progress of a runner when a play has been whistled dead.
- The line judge supervises player substitutions, the line of scrimmage during punts, and game timing. He notifies the referee when time has expired at the end of a quarter and notifies the head coach of the home team when five minutes remain for halftime. In the NFL, the line judge also alerts the referee when two minutes remain in the half. If the clock malfunctions or becomes inoperable, the line judge becomes the official timekeeper.
- The back judge ensures that the defensive team has no more than 11 players on the field and determines whether catches are legal, whether field goal or extra point attempts are good, and whether a pass interference violation occurred.
- The side judge mainly duplicates the functions of the back judge but is positioned twenty yards downfield from the line of scrimmage and opposite to the back judge.
- The field judge monitors and controls the play clock, counts the number of defensive players on the field, and watches for offensive pass interference and illegal use-of-hands violations by offensive players. He also makes decisions regarding catches, recoveries, the ball spot when a player goes out of bounds, and illegal touching of fumbled balls that have crossed the line of scrimmage.
Another set of officials, the chain crew, hold the chains that measure the 10 yards needed for a first down. The chain crew moves the chains up and down the field and keeps track of the current down using the down marker. This system has been used for over 100 years, is considered to be an accurate measure of distance, and is rarely subject to criticism from either side.
American football is played between two teams of 11 players each and uses an oval ball in the shape of a prolate spheroid. The game is played between two teams, one of which possesses the ball. The team in control of the ball, termed the offense, tries to advance the ball toward the end zone, the scoring area at either end of the field. The other team, termed the defense, tries to prevent the offense from advancing the ball.
A coin toss prior to the start of the game determines which team will have first possession of the ball. The game begins with a kickoff, in which the placekicker of the kicking team kicks the ball from a tee. A player from the receiving team catches the ball and runs towards the opposing end zone until he is tackled or steps out of bounds, at which point the ball is considered dead. The spot at which the ball becomes dead becomes the first line of scrimmage, and play begins from that point.
An official then places the ball on the field so that the long axis of the ball is parallel to the sidelines. It is placed at the middle of the field, between the two sets of hash marks, at the same distance from the goal line as where the previous play was declared dead. The teams line up on either side of the line of scrimmage or "neutral zone," which is a space that extends from sideline to sideline and is as wide as the length of the ball. Neither team may cross the neutral zone before the start of the play.
Leagues and tournaments
The National Football League (NFL) and the National Collegiate Athletic Association (NCAA) are the most popular football leagues in the United States. The National Football League (NFL) was founded in 1920 and has since become the largest and most popular sport in the United States. The NFL has the highest average attendance of any sporting league in the world, with an average attendance of almost 70,000 persons during the 2011 NFL Season. The NFL championship game, the Super Bowl, is among the biggest events in club sports worldwide. It is played between the champions of the National Football Conference (NFC) and the American Football Conference (AFC), and its winner is awarded the Vince Lombardi Trophy.
Collegiate football (NCAA) ranks third in overall popularity in the United States, after baseball. The NCAA is divided into three Divisions: Division I, Division II and Division III. Division I football is further divided into two subdivisions: the Football Bowl Subdivision (FBS) and the Football Championship Subdivision (FCS). The champions of Division I-FCS, Division II and Division III are determined through playoff systems, and the Division I-FBS champion is determined through the Bowl Championship Series (BCS). Division I-FBS will switch to a four-team playoff system in 2014.
Minor professional leagues
Several football leagues have been formed as rival leagues to the NFL. The XFL was created in 2001 by Vince McMahon and lasted for only one season. Despite television contracts with NBC and UPN and high expectations, the XFL suffered from poor television ratings and a low quality of play. The United Football League (UFL) has suspended its 2012 season, its fourth, due to financial issues. The United States Football League (USFL) operated for three seasons from 1983-1985 but collapsed due to poor business decisions and monetary problems. A subsequent USD $1.5 billion antitrust lawsuit against the NFL was successful in court, but the league was awarded only three dollars in damages. The World Football League (WFL) played for two seasons, in 1974 and 1975, but faced monetary issues so severe that the league could not pay its players. In its second and final season the WFL attempted to establish a stable credit rating, but the league disbanded before its second season could be completed.
The most successful minor league was the American Football League, which existed from 1960 to 1969. The AFL operated as a minor league from 1960 to 1964 and then signed a five-year, USD $36 million television deal with NBC and competed directly against the NFL. AFL teams signed NFL players to contracts, and their popularity grew to challenge that of the NFL. The two leagues merged in the 1970 season, and all AFL teams joined the NFL. An earlier minor league, the All-America Football Conference, was in play from 1946 to 1949. Two AAFC teams, the Cleveland Browns and the San Francisco 49ers, became members of the NFL.
Football leagues exist throughout the world, but the game has yet to achieve the international success and popularity of baseball and basketball. NFL Europa, the developmental league of the NFL, operated from 1991 to 1992 and then from 1995 to 2007. At the time of its closure, NFL Europe had five teams based in Germany and one in the Netherlands.
The European Football League (EFL), run by the European Federation of American Football (EFAF), is an annual invitational tournament between the champions or co-champions of competitions run by EFAF members. The league's championship game is the Eurobowl. Other EFAF tournaments include the EFAF Cup, played between the top teams from national leagues in a similar manner to the UEFA Cup, the Atlantic Cup, played between teams from the Atlantic region of Europe, and the Challenge Cup, played between teams from newer federations that are not eligible to play in the EFL or EFAF Cup. The International Federation of American Football (IFAF), an international body of American football federations, runs tournaments such as the IFAF World Championship, which is held every four years since 1999, the IFAF Women's World Championship, the IFAF U-19 World Championship and the Flag Football World Championship. The IFAF also organizes the annual International Bowl game. Football federations are also present in Asia, Oceania, and Pan America, and a total of 64 national football federations exist as of July 2012. At the international level, Canada, Mexico, and Japan are considered to be second-tier, while Austria, Germany, and France would rank among a third tier. All of these countries rank far below the United States, which is dominant at the international level.
Football is not an Olympic sport, but it was a demonstration sport at the 1932 Summer Olympics. The IFAF seeks recognition from the International Olympic Committee (IOC), which would be the second-to-last step to gaining admission to the Olympic Games themselves. It would take at least a decade to be admitted. Several major obstacles hinder the IFAF goal of achieving status as an Olympic sport: the predominant participation of men in international play, and the short three-week Olympic schedule. Large team sizes are an additional difficulty, due to the Olympics' set limit of 10,500 athletes and coaches. These issues are similar to those that rugby union faced prior to being admitted into the Olympics in the form of rugby sevens, a modified version of the sport, but football also has the issue of global visibility. Nigel Meville, the CEO of USA Rugby, noted that while rugby union has a major international presence through the International Rugby Board, "American football is recognized globally as a sport, but it's not played globally". In order to solve these concerns, major effort has been put into promoting flag football, a modified version of American football, at the international level.
Canadian football is related to American football, as both share roots in rugby football. Although Canadian football developed independently from American football, the two games have similar rules. In the Canadian variant, the field measures 150 yards by 65 yards, and it has 20-yard end zones. The main differences in rules are that the Canadian game has three downs instead of four, which results in a game that is more pass-oriented; there are twelve players on each side instead of eleven, and a single point is scored if the offensive team kicks the ball out of the defense's end zone. The Canadian Football League (CFL) is the major Canadian league and is the second-most popular sporting league in Canada, behind only the National Hockey League.
A major variant of American football is arena football, played by the Arena Football League (AFL). Arena football has eight-player teams and uses an indoor field 50 yards in length, excluding end zones, and 28.3 yards wide. Punting is illegal, and kickoffs are attempted from the goal line. Large overhead nets deflect forward passes and kicks that hit them, and deflected kicks are live balls that may be recovered by either team.
Below the Arena Football League are what New York Times writer Mike Tanier described as the "most minor of minor leagues:" indoor football leagues. Indoor leagues such as the Indoor Football League, Southern Indoor Football League, Ultimate Indoor Football League, Continental Indoor Football League and American Professional Football League are unstable. Their franchises regularly move from one league to another, merge with other teams, or dissolve entirely.
Flag football is a variation of American football in which players are not tackled, but a play is ruled dead once a "flag" attached the waist of the runner is pulled off. Touch football is a similar variant in which a play ends when the runner is touched. A game of touch football may require that the player be touched with either one hand or two, depending on the rules used.
- American football strategy
- Comparison of American football and rugby union
- Concussions in American football
- Fantasy football (American)
- Glossary of American football
- Homosexuality in American football
- List of American football stadiums by capacity
- List of American football players
- List of leagues of American and Canadian football
- Pro Football Hall of Fame
- Steroid use in American football
- Florio, Mike (July 27, 2012). "Football remains an Olympic long shot". Pro Football Talk. NBC Sports. Retrieved January 14, 2013.
- "American football". Oxford Advanced Learner's Dictionary. Oxford University Press. Retrieved November 18, 2012.
- "Spectators Guide to Rugby" (PDF). New England Rugby. Northeastern University. Retrieved November 24, 2012.
- "Rutgers - The Birthplace of Intercollegiate Football". Rutgers University. Retrieved November 24, 2012.
- No Christian End! The Beginnings of Football in America. Professional Football Researchers Association. Retrieved November 24, 2012.
- "Camp and His Followers". Professional Football Researchers Association. Retrieved November 24, 2012.
- Madden, John; Bill Gutman (2006). John Madden's Heroes of Football: The Story of America's Game. Dutton Children's Books. p. 7. ISBN 0-525-47698-9.
- Bennett (1976), pp 20
- Lewis, Guy M. (1969). "Teddy Roosevelt's Role in the 1905 Football Controversy". The Research Quarterly 40: 717–724.
- "The History of the NCAA". National Collegiate Athletic Association. Archived from the original on April 30, 2007. Retrieved November 24, 2012.
- Carroll, Bob. "Blondy Wallace and the Biggest Football Scandal Ever: 1906". The Coffin Corner (Professional Football Researchers Association). Retrieved November 25, 2012.
- "NFL History 1869–1910". NFL.com. Archived from the original
|url=(help) on January 2, 2008. Retrieved November 24, 2012.
- Danzig, Allison (1956). The History of American Football: Its Great Teams, Players, and Coaches. Englewood Cliffs, N.J.: Prentice-Hall. pp. 70–71.
- Vancil (2000) pp 22
- "The Birth of Pro Football". Pro Football Hall of Fame. Retrieved March 19, 2013.
- Clary, Jack (1994). "The First 25 Years". The Coffin Corner (Professional Football Researchers Association) 16 (4): 1, 4–5.
- Jozsa, Frank P. (2004). Sports Capitalism: The Foreign Business of American Professional Leagues. Ashgate Publishing. p. 270. ISBN 978-0-7546-4185-8. "Since 1922, [the NFL] has been the top professional sports league in the world with respect to American football"
- Nelson, Robert (January 11, 2007). "The Curse". Phoenix New Times. Retrieved January 30, 2013.
- "Greatest game ever played". Pro Football Hall of Fame. Retrieved March 20, 2013.
- Clary, Jack (1994). "The Second 25 Years". The Coffin Corner (Professional Football Researchers Association) 16 (5): 4–5.
- "BCS Chronology". FOX Sports on MSN. 2006. Archived from the original on September 15, 2007. Retrieved March 19, 2013.
- "Presidents get playoff plan right". ESPN.com. June 26, 2012. Retrieved March 20, 2013.
- "The Harris Poll: NFL continues 47-year run as America’s most popular sport". NFL Communications. January 17, 2013. Retrieved March 20, 2013.
- Harris, Nick (January 31, 2010). "Elite clubs on Uefa gravy train as Super Bowl knocked off perch". The Independent. Retrieved November 28, 2012.
- NFL Rules 2012, p. 21.
- NCAA Rules 2011–2012, p. 15.
- NFHS Rules 2012, p. 11.
- Merritt, Cam (April 27, 2011). "Can ten players be on the field without a penalty". LiveStrong.com. Retrieved October 5, 2012.
- NCAA Rules 2011–2012, p. 107.
- NFHS Rules 2012, p. 71–72.
- NFL Rules 2012, p. 21–22.
- NCAA Rules 2011–2012, p. 53–54.
- NFHS Rules 2012, p. 45–46.
- Dickson, James David (July 14, 2010). "The innovator". Michigan Today. Retrieved October 7, 2012.
- NCAA Rules 2011–2012, p. 21–22.
- NFHS Rules 2012, p. 16–17.
- "NFL in a nutshell". BBC Sport. October 19, 2005. Retrieved November 20, 2012.
- NFL Rules 2012, p. 21–24.
- NFHS Rules 2012, p. 57–58.
- NFL Rules 2012, p. 36, 40.
- Long, Howie; Czarnecki, John. "Common Penalties in American Football". Dummies.com. Retrieved November 23, 2012.
- "Football Players' Roles in Team Offense and Defense". Dummies.com. Retrieved January 14, 2013.
- Pasquarelli, Len (June 1, 2010). "Fullbacks back en vogue". ESPN.com. Retrieved November 22, 2012.
- Wood, Ryan. "Centers: The Unsung Heroes of Football". Active.com. Retrieved November 22, 2012.
- Long, Howie; Czarnecki, John. "Football's Offensive Team: The Receivers". Dummies.com. Retrieved November 22, 2012.
- Long, Howie; Czarnecki, John. "Football's Defensive Team: The Linebackers". Dummies.com. Retrieved November 23, 2012.
- Long, Howie; Czarnecki, John. "The Role of Special Teams in a Football Game". Dummies.com. Retrieved January 12, 2012.
- Long, Howie; Czarnecki, John. "Football Special Teams: Players on a Punt Team". Dummies.com. Retrieved January 12, 2012.
- NFL Rules 2012, p. 24–27.
- NCAA Rules 2011–2012, p. 22.
- NFHS Rules 2012, p. 17–19.
- "Head Injuries in Football". The New York Times. December 10, 2012. Retrieved January 16, 2013.
- Gregory, Sean (October 22, 2010). "Can Football Finally Tackle Its Injury Problem?". Time Magazine. Retrieved January 16, 2013.
- "Official Playing Rules and Casebook of the National Football League". National Football League. Retrieved 15 January 2013.
- "NCAA Rulebook". Retrieved 19 January 2013.
- "NFHS Rulebook". Retrieved 19 January 2013.
- "Pop Warner Little Scholars Rulebook". Retrieved 19 January 2013.
- Sackrowitz, Harold (2000). "Reﬁning the Point(s)-After-Touchdown Decision". Department of Statistical Science (Duke University) 13 (3): 29–30, 33–34. Retrieved October 23, 2012.
- NFL Rules 2012, p. 56–57.
- NCAA Rules 2011–2012, p. 77–79.
- NFHS Rules 2012, p. 65–66.
- NFL Rules 2012, p. 57–59.
- NCAA Rules 2011–2012, p. 79–80.
- NFHS Rules 2012, p. 66.
- "Beginner's Guide to Football". National Football League. Retrieved September 30, 2012.
- NFL Rules 2012, p. 60
- NFL Rules 2012, p. v, 1.
- NCAA Rules 2011–2012, p. 18–19, 23-24.
- NFHS Rules 2012, p. 11–12, 13, 28.
- NCAA Rules 2011–2012, p. 18.
- NFL Rules 2012, p. 2.
- NFHS Rules 2012, p. 14.
- NFL Rules 2012, p. 14.
- NCAA Rules 2011–2012, p. 45.
- NFHS Rules 2012, p. 38–39.
- NFHS Rules 2012, p. 39.
- "How Football Game Time Is Measured in Quarters". Dummies.com. Retrieved December 2, 2012.
- NFL Rules 2012, p. 14–18
- NCAA Rules 2011–2012, p. 47–53.
- NFHS Rules 2012, p. 38–45
- McCarthy, Michael (October 27, 2011). "Delay of game: NFL games running longer in 2011". USA Today. Retrieved December 3, 2012.
- NCAA Rules 2011–2012, p. 16, 41.
- NCAA Rules 2011–2012, p. 41, 46-47.
- NFHS Rules 2012, p. 36, 45.
- Branch, John (December 31, 2008). "The Orchestration of the Chain Gang". The New York Times. Retrieved December 19, 2012.
- St. John, Allan (December 18, 2009). "The Tech Behind the Football's Broadcast-Only First Down Line: The Tech Behind the Football's Broadcast-Only First Down Line". Popular Mechanics. Retrieved 2 November 2012.
- Hogrogian, John (1999). "The Last Drop Kick?". The Coffin Corner (Professional Football Researchers Association) 21 (6). Retrieved October 22, 2012.
- "The last dropkick". Pro Football Hall of Fame. Retrieved October 8, 2012.
- NFL Rules 2012, p. 50.
- NCAA Rules 2011–2012, p. 34.
- NFHS Rules 2012, p. 32.
- NFL Rules 2012, p. 6.
- NCAA Rules 2011–2012, p. 30.
- NFHS Rules 2012, p. 27.
- NFL Rules 2012, p. 8–9.
- NFHS Rules 2012, p. 31–32.
- NFL Rules 2012, p. 29–30.
- NCAA Rules 2011–2012, p. 61–64.
- NFHS Rules 2012, p. 15, 46, 52-53.
- NFL Rules 2012, p. 33–34, 50-53.
- NCAA Rules 2011–2012, p. 55–56, 63-64.
- NFHS Rules 2012, p. 49, 53-54.
- NFL Rules 2012, p. 7, 54-55.
- NCAA Rules 2011–2012, p. 30, 66-67.
- NFHS Rules 2012, p. 27, 56.
- Long, Howie; Czarnecki, John. "American Football Officials". Dummies.com. Retrieved November 22, 2012.
- NFL Rules 2012, p. 3.
- Fentress, Andrew (May 18, 2012). "New version of United States Football League aims to succeed where others have failed". Oregon Live. Advance Internet. Retrieved January 9, 2013.
- "NFL founded in Canton". Pro Football Hall of Fame. Retrieved November 26, 2012.
- Chin, Andrew (November 25, 2012). "China fast catching American football fever with 10 teams formed". South China Morning Post. Retrieved November 26, 2012.
- "And the silver goes to ...". The Economist. September 27, 2011. Retrieved December 6, 2012.
- George, Shannon (September 10, 2009). "Let's Learn About: The Vince Lombardi Trophy". Pittsburgh Post-Gazette. Retrieved January 9, 2013.
- "Football is America's Favorite Sport as Lead Over Baseball Continues to Grow". Harris Interactive. January 25, 2005. Retrieved November 26, 2012.
- "About the NCAA". NCAA.org. Retrieved January 9, 2013.
- "Differences Among the Three Divisions: Division I". NCAA.org. Retrieved January 9, 2013.
- "Postseason Football". NCAA.org. Retrieved January 9, 2013.
- Sandomir, Richard (May 11, 2001). "No More Springtimes for the XFL as League Folds". The New York Times. Retrieved January 20, 2013.
- Keiser, Thomas (October 20, 2012). "Just What Is Going on with the UFL?". International Business Times. Retrieved January 20, 2013.
- Somers, Kent (August 7, 2008). "Twenty years later, USFL still brings fond memories". USA Today. Retrieved March 25, 2013.
- Johnson, William Oscar (December 1, 1975). "The Day The Money Ran Out". Sports Illustrated. Retrieved March 25, 2013.
- Cross, B. Duane (January 22, 2001). "Off-the-field competition yields game-changing merger". CNNSI. Retrieved February 15, 2013.
- Nelson, David M. (December 12, 1993). The Anatomy of a Game: Football, the Rules, and the Men Who Made the Game (1 ed.). University of Delaware Press. p. 15. ISBN 978-0874134551. Retrieved March 28, 2013.
- "NFL Europa to cease operations". NFL.com. June 29, 2007. Archived from the original
|url=(help) on July 3, 2007. Retrieved January 9, 2013.
- "European Football League EFL". European Federation of American Football. Retrieved January 9, 2013.
- "EFAF Cup". European Federation of American Football. Retrieved January 9, 2013.
- "Atlantic Cup". European Federation of American Football. Retrieved January 9, 2013.
- "Challenge Cup". European Federation of American Football. Retrieved January 9, 2013.
- "Championship Competitions". International Federation of American Football. Retrieved January 9, 2013.
- Breer, Albert (July 26, 2012). "Football in Olympics is a dream that could become a reality". NFL.com. Retrieved March 21, 2013.
- "Gridiron football". Encyclopædia Britannica Online. pp. 1, 13–14. Retrieved January 10, 2013.
- Buchinski, Colin; Neu, Dietrich (January 6, 2011). "Head to Head: CFL vs. NFL". The Carillon. Retrieved January 10, 2013.
- Colston, Chris (April 15, 2007). "Arena football: Is it America's fifth major sport?". USA Today. Retrieved January 10, 2013.
- "Arena football: The basics". USA Today. April 13, 2007. Retrieved January 10, 2013.
- Tainer, Mike (June 27, 2011). "Staying in the Game on Football's Fringe". The New York Times. Retrieved January 19, 2013.
- "Flag football". Miriam-Webster Learner's Dictionary. Retrieved January 10, 2013.
- "Touch football". Miriam-Webster Learner's Dictionary. Retrieved January 10, 2013.
- Gay, Jason. "The 32 Rules of Thanksgiving Touch Football". The Wall Street Journal. Retrieved January 10, 2013.
- "Official Playing Rules and Casebook of the National Football League" (PDF). National Football League. 2012.
- Redding, Rogers (2011–2012). Halpin, Ty, ed. "NCAA Football Rules and Interpretations" (PDF). National Collegiate Athletic Association. ISSN 0736-5144.
- Colgate, Bob, ed. (2011). "2011 NFHS Football Rules Book" (PDF). Gardener, Robert B.. NFHS Publications.
|Look up american football in Wiktionary, the free dictionary.|
|Wikimedia Commons has media related to: American football|
- The Official Site of the National Football League
- The Official Site for NCAA Football
- The Official Site of the International Federation of American Football
- NFL 360, an introductory website to football rules
- Excerpts of a 1903 football game between the University of Chicago and the University of Michigan
- American Football at the Open Directory Project