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
Comparison of American football and rugby union only one of the three being on the field at a time. That is to say that in professional American football, the majority of players play in only one specialization (or "one side of the ball") – however, every player is eligible to play in any specialization. In rugby the teams are divided into eight forwards and seven backs. Both groups of players partake in attacking and defensive plays and are on the pitch at the same time. Only the eight forwards take part in the "set pieces", which are ways to contest ball possession when there is a minor