美式足球(football (gridiron))
盛行於美国和加拿大的一种球类运动。在美国，由两队（每队11人）在两端有球门柱的长方形场地上比赛，每队藉着持球或传球给队友设法使椭圆形的球越过对方得分线达阵或设法将球踢进球门柱之间而得分。在比赛中拿球的一方有4次进攻（down）的机会，必须在4次进攻中将球至少推进10码，便可再获得4次进攻机会，否则就换对方进攻。计分方式有：持球或完成传球越过得分线（达阵成功）得6分，把球踢过球门（射门）得3分；达阵得分後可再加踢一球额外得1分，或持球跑过、传球越过得分线可附加得2分。美式足球是在19世纪时由英式橄榄球和足球混合演变而成。1869年在新泽西州举办第一次校际比赛，参赛的两队是普林斯顿大学与拉特格斯（Rutgers）学院。1873年订定最早的校际比赛规则，并组成常春藤联盟。此後美式足球运动在美国大学间流行起来。1998年起全国大学生体育协会从全国的球队中选出战绩最好的两个队伍举行季後赛，赢的一队可以得到全国冠军奖杯。职业美式足球始於1890年代，但直到第二次世界大战後才成为美国主要的运动。1922年美国职业美式足球协会改组为全国美式足球联盟（NFL），对立的美国美式足球联盟（AFL）建立於1959年，但1966年的协议导致1970年两个联盟在全国美式足球联盟名下合并，现分为美国联会和国家联会，两联会的优胜者竞争超级盃美式足球赛冠军。在俄亥俄州的广州建有美国职业足球名人堂。加拿大式足球与美式足球略有不同：加拿大式足球每队12人，而不是11人；球场较大，比赛中拿球的一方只有3次进攻机会；比较强调传球，打法更开阔。亦请参阅Canadian Football League。
English version：
football (gridiron)
Game played predominantly in the United States and Canada. In the United States, it is played between two teams of 11 players each on a rectangular field having two goalposts at each end, whose object is to get an oblong ball, in possession of one side at a time, over a goal line or between goalposts by running, passing, or kicking. A team must advance the ball 10 yards in four attempts (called downs), in order to continue to have the ball for another four downs. A run or completed pass over the goal line (touchdown) counts as six points. A kick through the goalposts (field goal) counts as three points. A post-touchdown goal kick, or extra point, counts as one point; two points are awarded if the ball is run or passed over the goal line. Gridiron football (so-called because of the markings on the field) evolved in the 19th century as a combination of rugby and soccer. The first intercollegiate match was played in 1869 between Princeton University and Rutgers College. In 1873 the first collegiate rules were standardized and the Ivy League was formed. Collegiate football grew into one of the most popular U.S. sports. In 1998 the National Collegiate Athletic Association implemented a point plan for picking the country's top two teams, which would meet in a post-season national championship game. Professional football began in the 1890s but did not become a major sport until after World War II. The National Football League was formed (from an earlier association) in 1922; in 1966 it subsumed the rival American Football League (created in 1959). The NFL is now divided into an American and a National conference; the conference winners compete for the Super Bowl championship. A Football Hall of Fame is located in Canton, Ohio. Canadian football differs from U.S. football principally by having 12 players on a team rather than 11, employing a larger field, and allowing only three downs to make a first down. These variations cause a more wide-open style of game, with emphasis on passing. See also Canadian Football League.