American football American football American football, referred to as football in the United States and Canada and also known as gridiron, is a team sport played by two teams of eleven players on a rectangular field with goalposts at each end. The offense, which is the team controlling the oval-shaped football, attempts to advance down the field by running with or passing the ball, while the defense, which is the team without control of the ball, aims to stop the offense's advance and aims to take control of the ball for themselves. The offense must advance at least ten yards in four
Uniform number (American football) determining possible rules infractions by players. Under current rules in all three of the most prominent levels of American football (high school football, college football and professional football), all players must wear a number from 1 to 99, and no two players on the same team may wear the same number on the field at the same time. In the past, players have used the numbers 0, 00 and, in two special cases, 100. Those who wear numbers from 50 to 79 are, by rule, playing in specific positions which are prohibited from catching or touching forward passes if their