Scoring (dark jersey) scores a touchdown while a defender from the
Tulsa Golden Hurricane (in white) looks on. The goal line is marked by the small orange pylon. In football, the winner is the team that has scored more points at the end of the game. There are multiple ways to score in a football game. The
touchdown (TD), worth six points, is the most valuable scoring play. A touchdown is scored when a live ball is advanced into, caught, or recovered in the opposing team's end zone. A
field goal (FG), worth three points, is scored when the ball is place kicked or drop kicked through the uprights and over the crossbars of the defense's goalposts. Almost all field goal attempts are done via place kick. While drop kicks were common in the early days of the sport, the shape of modern footballs makes it difficult to reliably drop kick the ball. The last successful scoring play by drop kick in the NFL was accomplished in 2006; prior to that, the last successful drop kick had been made in 1941. After a PAT attempt or successful field goal, the scoring team must kick the ball off to the other team. A
safety is scored when the ball carrier is tackled in the carrier's own end zone. Safeties are worth two points, which are awarded to the defense. Safeties are the least common method of scoring in football.
Field and equipment in
St. Louis as seen from behind one end zone. The tall, yellow goal posts mark where the ball must pass for a successful field goal or extra point. The large, rectangular area marked with the team name is the end zone. Football games are played on a rectangular
field that measures long and wide. Lines marked along the ends and sides of the field are known as the end lines and
sidelines.
Goal lines are marked inward from each end line. Weighted pylons are placed along each sideline, on the inside corner of the intersections with 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 increments.
Yard lines, which can run the width of the field, are marked every . A one-yard-wide line 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 distance from the closest goal line in yards are placed on both sides of the field every ten yards. The
football itself is a
prolate spheroid leather ball, similar to the balls used in rugby or
Australian rules football. At all levels of play, the football is inflated to , or just under one atmosphere, and weighs ; beyond that, the exact dimensions vary slightly. In professional play the ball has a long axis of , a long circumference of , and a short circumference of . 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 followed by a short break. Before the game starts, the referee and each team's
captain meet at midfield for a
coin toss. The visiting team can call either "heads" or "tails"; the winner of the toss chooses whether to receive or kick off the ball or which goal they wish to defend. They can defer their choice until the second half. Unless the winning team decides to defer, the losing team chooses the option the winning team did not select—to receive, kick, or select a goal to defend to begin the second half. Most teams choose to receive or defer, because choosing to kick the ball to start the game allows the other team to choose which goal to defend. 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. If certain fouls are committed during play while time has expired, the quarter may be extended through an
untimed down. Games last longer than their defined length due to play stoppages—the average NFL game lasts slightly 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
play clock is used to show the amount of time within which the offense must initiate a play. The play clock is set to 25 seconds after certain administrative stoppages in play and to 40 seconds when play is proceeding without such stoppages. If the offense fails to start a play before the play clock reads "00", a
delay of game foul is called on the offense.
Advancing the ball and downs quarterback
Jake Delhomme (number 17) in the motion of throwing a forward pass There are two main ways the offense can advance the ball:
running and
passing. In a typical play, the center passes the ball backwards and between their legs to the quarterback in a process known as the
snap. The quarterback then either hands the ball off to a running back, throws the ball, or runs with it. 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. A forward pass can be legally attempted only if the passer is behind the line of scrimmage; only one forward pass can be attempted per down. In the NFL, a down also ends immediately if the runner's helmet comes off. 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 football is turned over to the defense. In most situations, if the offense reaches their fourth down they will
punt the ball to the other team, which forces them to begin their drive from farther down the field; if they are in
field goal range, they might attempt to score a field goal instead. The spot needed to secure a first down is known as the line to gain. On television, a yellow line is electronically superimposed on the field to show the line to gain to the viewing audience.
Kicking 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 a tee; 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. The ball may be recovered by the kicking team once it has gone at least ten yards and has touched the ground or has been touched by any member of the receiving team. The three types of scrimmage kicks are place kicks, drop kicks, and punts. Only place kicks and drop kicks can score points. because the pointy shape of the football makes it difficult to reliably drop kick. The kicking team is prohibited from interfering with the receiver's opportunity to catch the ball. The receiving team has the option of signaling for a
fair catch, which prohibits the defense from blocking into or tackling the receiver. The play ends as soon as the ball is caught, and the ball may not be advanced.
Officials and fouls and
Cal Berkeley use the chains to measure for a first down. Here, the ball is just short of the pole and therefore short of a first down. 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
foul has been called. An official who spots multiple fouls will throw their hat as a secondary signal. Women can serve as officials;
Sarah Thomas became the NFL's first female official in 2015. The seven officials (of a standard seven-man crew; lower levels of play up to the college level use fewer officials) on the field are each tasked with a different set of responsibilities: • The referee: is positioned behind and to the side of the offensive backs. The referee is charged with oversight and control of the game and is the authority on the score, the down number, and any rule interpretations in discussions among the other officials. The referee 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 referee positions themselves to the passing arm side of the quarterback. In most games, the referee is responsible for spotting the football prior to a play from scrimmage. • The umpire: is positioned in the defensive backfield, except in the NFL, where the umpire is positioned lateral to the referee on the opposite side of the formation. The umpire watches play along the line of scrimmage to make sure that no more than 11 offensive players are on the field before the snap, and that no offensive linemen are
illegally downfield on pass plays. The umpire monitors 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 game score. They also assist the referee in situations involving possession of the ball close to the line of scrimmage, determine whether player equipment is legal, and dry wet balls prior to the snap if a game is played in rain. • The back judge: is positioned deep in the defensive backfield, behind the umpire. 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 back judge is also responsible for the play clock, the time between each play, when a visible play clock is not used. • The head linesman/down judge: is positioned on one end of the line of scrimmage. The head linesman/down judge 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/down judge also rules on out-of-bounds calls that happen on their side of the field, oversees the chain crew, and marks the forward progress of a runner when a play has been whistled dead. • The side judge: is positioned twenty yards downfield of the head linesman. The side judge mainly duplicates the functions of the field judge. On field goal and extra point attempts, the side judge is positioned lateral to the umpire. • The line judge: is positioned on the end of the line of scrimmage, opposite the head linesman. They supervise player substitutions, the line of scrimmage during punts, and game timing. The line judge 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 field judge: is positioned twenty yards downfield from the line 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. The field judge 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. On field goal and extra point attempts, the field judge is stationed under the upright opposite the back judge. • The center judge: is an eighth official used only in the top level of college football. The center judge stands lateral to the referee, the same way the umpire does in the NFL. The center judge is responsible for spotting the football after each play and has many of the same responsibilities as the referee, except announcing penalties. Another set of officials, the
chain crew, are responsible for moving the chains. The chains, consisting of two large sticks with a 10-yard-long chain between them, are used to measure for a first down. The chain crew stays on the sidelines during the game, but if requested by the officials, they will briefly bring the chains onto the field to measure. A typical chain crew will have at least three people—two members of the chain crew will hold either of the two sticks, while a third will hold the down marker. The down marker, a large stick with a dial on it, is flipped after each play to indicate the current down and is typically moved to the approximate spot of the ball. The chain crew system has been used for over 100 years and is considered an accurate measure of distance, rarely subject to criticism from either side. ==Safety and brain health==