Footbal Americano

American football, known as football in the United States, is a team sport played between two teams of 11 players with an oval ball[2] on a rectangular field 120 yards long and 53.3 yards wide with goalposts at either end. The team in possession of the ball (the offense) attempts to advance down the field by running with or passing the ball. In order to continue their drive, the offense mustadvance 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, but if they fail, 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 place or drop kicking the ball through the opponent's goalpost (a field goal), while thedefense 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), with the first game playedon November 6, 1869. Rule changes from 1880 on by Walter Camp included the snap, 11-a-side teams and downs; further rule changes legalized the forward pass and created the neutral zone along the width of the football. Today, American football is the most popular sport in the United States, where the National Football League (NFL) is the most popular league. The league's championship, the Super Bowl, is amongthe most-watched club sporting events in the world.
American football is played between two teams of 11 players each, with an oval (specifically prolate spheroid[15]) ball.[2] The basic format of the game involves two teams, one of which is in possession of the ball. The team in possession of the ball, termed the offense, tries to advance the ball towards the end zone, the scoring area at eitherend of the field. The other team, termed the defense, tries to stop the offense and prevent them from advancing the ball.[16] A game begins with a kickoff; the kicking and receiving teams are determined by a pre-game coin toss. The kickoff occurs as a player on the kicking team (the placekicker) kicks the ball from a tee. The receiving team then catches the ball and runs towards the opposing endzone until they are tackled or step out of bounds, at which point the ball is considered dead. The point where the ball becomes dead is defined as the first line of scrimmage, and play begins from that point.
Advancement of the ball occurs as a series of up to four discrete plays or downs. The offense must gain at least 10 yards in the four downs to continue advancing the ball. Before the startof the play, an official places the ball on the field so that the long axis of the ball is parallel to the sidelines. It is placed on or between the two sets of hash marks along the line, parallel to the goal line, where the previous play was declared dead. The two teams line up on either side of the line of scrimmage or "neutral zone", which is defined as the space as wide as the length of theball extending from sideline to sideline parallel to the goal lines. Neither team may cross this neutral zone before the start of the play. A play begins with the snap, which occurs when the ball is lifted from the ground by one player on the offense (the center) and passed backwards to a second player (usually the quarterback). Play then continues until the ball becomes dead, at which pointthe down is considered over. If the player was tackled, steps out of bounds or his forward progress was stopped, the ball is placed at the spot of the tackle or where the player stepped out of bounds. If the ball became dead from an incomplete forward pass, the ball is placed at the same place it was at the start of the prior down. If the play resulted in a first down, a new set of four downs are given...