|
Game play in American football consists of a series of ''downs'', individual plays of short duration, outside of which the ball is ''dead'' or not in play. These can be plays from scrimmage – passes, runs, punts, or field goal attempts (from either a place kick or a drop kick) – or free kicks such as kickoffs and fair catch kicks. Substitutions can be made between downs, which allows for a great deal of specialization as coaches choose the players best suited for each particular situation. During a play, each team should have no more than 11 players on the field, and each of them has specific tasks assigned for that specific play. ==Objective of the game== The objective of this game is to score more points than the other team during the allotted time.〔(【引用サイトリンク】url=https://files.nyu.edu/rk1193/public/Objectives_Basics_Field.html )〕 The team with the ball (the ''offense'') has 4 plays (''downs'') to advance at least 10 yards, and can score points once they reach the opposite end of the field, which is home to a scoring zone called the ''end zone'', as well as the goal posts. If the offense succeeds in advancing at least 10 yards, they earn a "first down" and the number of tries allotted is reset and they are again given 4 tries to advance an additional 10 yards, starting from the spot to which they last advanced. If the offense does not advance at least 10 yards during their 4 downs, the team without the ball (the ''defense'') regains control of the ball (called ''turnover on downs''). On offense, points are scored by advancing the ball into the opponent's end zone for a ''touchdown'' (worth six points), or by kicking the ball from the playing field through the raised vertical posts (the ''goal posts'') which are most commly situated on the end line of the end zone for a ''field goal'' (worth three points). After scoring a touchdown, the offense is given an additional opportunity from the 2-yard line (3-yard line in amateur football) to attempt to score (in the NFL, 15-yard line on 1-point conversions). Conversion attempts are used to score 1 or 2 points as follows: * The offense may attempt a field goal kick which is worth 1 point. * The offense may attempt to re-advance the ball into the opponent's end zone for a ''two-point conversion'' worth 2 points. While the opposing team has possession, the defense attempts to prevent the offense from advancing the ball and scoring. If an offensive player loses the ball during play (a ''fumble'') or the ball is caught by a defensive player while still in the air (an ''interception''), the defense may attempt to run into the offense's end zone for a touchdown. The defense may also score points by tackling the ball carrier in the offense's own end zone, called a ''safety'' (which is worth two points). 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「American football rules」の詳細全文を読む スポンサード リンク
|