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American football

2007 Schools Wikipedia Selection. Related subjects: Sports

   The ball used in American football has a pointed prolate spheroid or
   vesica piscis shape, and usually has a large set of stitches along one
   side.
   Enlarge
   The ball used in American football has a pointed prolate spheroid or
   vesica piscis shape, and usually has a large set of stitches along one
   side.

   American football, known in the United States and Canada simply as
   football, is a competitive team sport. The object of the game is to
   score points by advancing the football into the opposing team's end
   zone. The ball can be advanced by carrying the ball, or by throwing or
   handing it from one teammate to the other. Points can be scored in a
   variety of ways, including carrying the ball over the goal line,
   throwing the ball to another player past the goal line or kicking it
   through the goal posts on the opposing side. The winner is the team
   with the most points when the time expires and the last play ends.
   However, tied games can occur.

   Outside of the United States and Canada, the sport is usually referred
   to as American football (or sometimes as gridiron or gridiron football)
   to differentiate it from other football games.

Popularity

   American football is the most popular spectator sport in the United
   States. In surveys of Americans, pluralities of respondents consider it
   to be their favorite sport. Football's American TV viewership ratings
   far surpass those of other sports.

   The 32-team National Football League (NFL) is the only major
   professional American football league. Its championship game, the Super
   Bowl, is watched by nearly half of U.S. television households and is
   also televised in over 150 other countries. The day of the game, Super
   Bowl Sunday is a day when many fans host game watching parties and
   invite friends and family over to eat and watch the game. It is
   considered by many to be the year's biggest day for "stay at home
   parties."
   A Colorado State University player runs with the ball as an Air Force
   Academy player lines up a tackle.
   Enlarge
   A Colorado State University player runs with the ball as an Air Force
   Academy player lines up a tackle.

   College football is also popular throughout North America. Four college
   football stadiums ( Michigan Stadium, Beaver Stadium, Neyland Stadium,
   Ohio Stadium), seat more than 100,000 fans and regularly sell out. Even
   high school football games can attract more than 10,000 people in some
   areas. The weekly autumn ritual of college and high-school
   football—which includes marching bands, cheerleaders and parties
   (including the ubiquitous tailgate party)—is an important part of the
   culture in much of smalltown America. It is a long-standing tradition
   in the United States (though not universally observed) that high school
   football games are played on Friday, college games on Saturday, and
   professional games on Sunday (with an additional professional game on
   Monday nights).

   Certain fall and winter holidays—most notably Thanksgiving and New
   Years' Day—have traditional football games associated with them.

   Football is played recreationally by amateur club and youth teams
   (e.g., the Pop Warner little-league programs). There are also many
   "semi-pro" teams in leagues where the players are paid to play but at a
   small enough salary that they generally must also hold a full-time job.

   The NFL operates a developmental league, NFL Europa, with teams in five
   German cities and one in the Netherlands. The professional Canadian
   Football League plays under Canadian rules. The sport is popular as an
   amateur activity in Mexico and American Samoa and to a lesser extent in
   Japan, Europe, Korea, New Zealand and Australia.

   Organized football is played almost exclusively by men and boys,
   although a few amateur and semi-professional women's leagues have begun
   play in recent years.

Rules

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

Field and players

   The numbers on the field indicate the number of yards to the nearest
   end zone.
   Enlarge
   The numbers on the field indicate the number of yards to the nearest
   end zone.
   Los Angeles Memorial Coliseum, a large American Football stadium
   Enlarge
   Los Angeles Memorial Coliseum, a large American Football stadium

   American football is played on a rectangular field 120 yards (110
   meters) long by 53 1/3 yards (49 meters) 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 apart. A
   scoring area called an end zone extends 10 yards beyond each goal line
   to each end line.

   Yard lines cross the field every 5 yards, and are numbered 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 side lines 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 goal posts (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 (3 m) 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 almost all of the 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.

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). 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

   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 towards their opponent's (the defense's) end zone.
   When the offense gains 10 yards, it gets a first down, or another set
   of four downs to gain 10 yards. If the offense fails to gain a first
   down (10 yards) after 4 downs, it loses possession of the ball.

   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 centre, then passes (or
   "snaps") the ball between his legs to a teammate, usually the
   quarterback.

   Players can then advance the ball in two ways:
    1. By running with the ball, also known as rushing. One ball-carrier
       can hand the ball to another; this is known as a handoff.
    2. 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 on a play
       and only from behind the line of scrimmage. The ball can be thrown,
       pitched, or tossed sideways or backwards at any time. This type of
       pass is known as a lateral and is less common in American football
       than in rugby league or rugby union, where only backwards passes
       are permitted.

   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 out of bounds or touches the ground before it
       is caught. This is known as an incomplete pass. The ball is
       returned to the original line of scrimmage for the next down.
     * The ball or the player with the ball goes beyond the dimensions of
       the field (out of bounds).
     * A team scores.

   Officials blow a whistle to notify all 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 happens:
     * The team fails to get a first down— i.e., they fail to move the
       ball forward at least 10 yards in four downs. The defensive team
       takes over the ball at the spot where the play ends. A change of
       possession in this manner is commonly called a turnover on downs.
     * The offense scores a touchdown or field goal. The team that scored
       then kicks off the ball to the other team.
     * The offense punts the ball to the defense. A punt is a kick in
       which a player drops the ball and kicks it before it hits the
       ground. Punts are nearly always made on fourth down, when the
       offensive team does not want to risk giving up the ball to the
       other team at its current spot on the field (through a failed
       attempt to make a first down) and feels it is too far from the
       other team's goal 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 or forced out of bounds. After
       the intercepting player is tackled or forced out of bounds, his
       team's offensive unit returns to the field and takes over at his
       last position.
     * 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.
       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 of the end zone, the other team gets
       the ball at its own 20-yard line (that is, 20 yards from the end
       zone).
     * An offensive ballcarrier is tackled, forced out of bounds, loses
       the ball out of bounds, or commits certain penalties in his own end
       zone. This rare occurrence is called a safety.

Scoring

   A team scores points by the following plays:
     * A touchdown (TD) is worth 6 points. It is scored when a player runs
       the ball into or catches a pass in his opponent's end zone. A
       touchdown is analogous to a try in rugby 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 line (the 2-yard 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)), or run
            or pass it into the end zone in the manner of a touchdown for
            2 points (a two-point conversion).
     * A field goal (FG) is worth 3 points, and it is scored by kicking
       the ball over the crossbar and through the goal posts. 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). 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 is worth 2 points. A safety is scored by the defense when
       the offensive player in possession of the ball is forced back into
       his own end zone and is tackled there, fumbles the ball out of the
       end zone, or commits intentional grounding in the end zone. Certain
       penalties (primarily blocking fouls) by the offense occurring in
       the end zone also result in a safety.

Kickoffs and free kicks

   Each half begins with a kickoff. Teams also kick off after scoring
   touchdowns and field goals. The ball is kicked from a kicking tee,
   which is made from the team's own 30-yard line in the NFL and from the
   35-yard line in college football. 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 the end zone. Punts and turnovers in the end
   zone can also end in touchbacks.

   After safeties, the team that gave up the 2 points puts the ball into
   play with a punt or placekick from its own 20-yard line.
   A halfback leads fellow backs through an agility drill
   Enlarge
   A halfback leads fellow backs through an agility drill

Penalties

   Rule violations are punished with penalties. Most penalties result in
   moving the football either towards the defense's endzone in the case of
   a defensive penalty, or away from the defense's endzone in the case of
   an offensive penalty. Some defensive penalties give the offense an
   automatic first down. In addition, if a penalty gives the offensive
   team enough yardage to gain a first down, they get a first down as
   usual. If a penalty occurs during a play, an official throws a yellow
   flag near the spot of the foul; additional penalties are signalled by
   the same official by throwing a beanbag or his hat. When the play is
   over, the team that did not commit the penalty has the option of taking
   either the penalty and replaying the down, or the result of the play
   and advancing to the next down.

   A few of the most-common penalties include:
     * False start: An offensive player illegally moves after lining up
       for the snap.
     * Offsides: A defensive player is on the wrong side of the ball at
       the start of a play.
     * Holding: Illegally grasping or pulling an opponent other than the
       ball-carrier.
     * 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.
     * Illegal Block in the Back: An offensive player pushing a player
       from the opposite team in the back.

Variations

   Some 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. Professional,
   intercollegiate, and varsity-level high school football invariably use
   the standard tackling rules.

Players

   Most football players have highly specialized roles. At the college and
   NFL levels, most play only offense or only defense.

Offense

     * The offensive line consists of five players whose job is to protect
       the passer and clear the way for runners by blocking members of the
       defense. Except for the centre, offensive linemen generally do not
       handle the ball.
     * The quarterback (QB) receives the ball on most plays. He then hands
       or tosses it to a running back, throws it to a receiver or runs
       with it himself.
     * Running backs line up behind or beside the QB and specialize in
       rushing with the ball. They also block, catch passes and, on rare
       occasions, pass the ball to others.
     * Wide receivers line up near the sidelines. They specialize in
       catching passes.
     * Tight ends 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).

   Not all of these types of players will be in on every offensive play.
   Teams can vary the number of wide receivers, tight ends and running
   backs on the field at one time.

Defense

     * The defensive line consists of three to six players who line up
       immediately across from the offensive line. They try to tackle the
       running backs before they can gain yardage or the quarterback
       before he can throw a pass.
     * In most situations, at least three players line up as defensive
       backs (commonly known as safeties or cornerbacks). They cover the
       receivers and try to stop pass completions. They occasionally rush
       the quarterback.
     * The other players on the defense are known as linebackers. They
       line up between the defensive line and defensive backs and may
       either rush the quarterback or cover potential receivers.

Special teams

   The units of players who handle kicking plays are known as " special
   teams". Two important special-teams players are the " punter", who
   handles punts, and the " placekicker" or "kicker", who kicks off and
   attempts field goals and extra points.

Basic strategy

   To some fans, the chief draw of football is the strategy that goes on
   between the two coaching staffs. Each team has a playbook of dozens to
   hundreds of plays. Ideally, each play is a scripted, strategically
   sound team-coordinated endeavour. 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. 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.

   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 (see below) of football, is
   why teams play at most one game per week.

Physicality

   American football is a contact sport. To stop the offense from
   advancing the ball, the defense must tackle the player with the ball by
   knocking 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, punch or trip 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.

   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.
   Unfortunately, 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, with
   less severe impacts and less injuries. Better helmets have allowed
   players to use their helmets as weapons. 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, twenty-eight football players, mostly
   high schoolers, died from injuries directly related to football from
   2000-05, according to the National Centre for Catastrophic Sport Injury
   Research. Concussions are common, with about 41,000 suffered every year
   among high school players according to the Brain Injury Association of
   Arizona.

   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.

History

   Both American football and soccer have their origins in varieties of
   football played in the United Kingdom in the mid-19th century, and
   American football is directly descended from rugby football.

   Rutgers University and Princeton University, played the first game of
   college football on Nov. 6, 1869 in New Brunswick, N.J. Rutgers won
   that first game, 6-4.

   Encouraged by Yale University's Walter Camp, the schools began to adopt
   rules that would differentiate American football from rugby in the
   1880s. The scrimmage was introduced in 1880 and the system of downs in
   1882.

   By the turn of the 20th century, football had become notoriously
   dangerous; 18 college players died in 1905 alone. Colleges responded
   with a series of rule changes to open up the game, most importantly the
   forward pass, along with outlawing dangerous formations such as the "
   flying wedge", and introducing and requiring better equipment such as
   helmets.

   The game had achieved its modern form by 1912, when the field was
   changed to its current size, the value of a touchdown increased to 6
   points, and a fourth down added to each possession. Originally
   dominated by the Ivy League, football soon captured the interest of
   colleges nationwide. By 1916, when the Rose Bowl game matching eastern
   and western teams became an annual event, football had developed a
   national following second only to baseball among team sports.

   Professional football developed in the mill towns of Pennsylvania and
   the American Midwest in the early years of the 20th century. The NFL
   was founded in 1920 in Canton, Ohio. Professional football remained a
   largely regional sport of secondary importance until after World War
   II. Television broadcasts greatly enhanced NFL football's national
   appeal, and the pro game surpassed both college football and baseball
   in popularity in the 1960s. The first Super Bowl—between the champions
   of the NFL and the rival American Football League—was played in 1967,
   and the two leagues merged in 1970.

   Retrieved from " http://en.wikipedia.org/wiki/American_football"
   This reference article is mainly selected from the English Wikipedia
   with only minor checks and changes (see www.wikipedia.org for details
   of authors and sources) and is available under the GNU Free
   Documentation License. See also our Disclaimer.
