American football positions
In American football, the specific role that a player takes on the field is referred to as their "position". Under the modern rules of American football, both teams are allowed 11 players on the field at one time and have "unlimited free substitutions", meaning that they may change any number of players during any "dead ball" situation. This has resulted in the development of three task-specific "platoons" of players within any single team: the offense, the defense, and "special teams". Within these three separate "platoons", various positions exist depending on the jobs that the players are doing.
The offensive line (on left, in orange jerseys) consists of a center (with ball in hand ready to snap) with two guards on either side, and two tackles.
A wide receiver (No. 87, in white) begins a play in the flanker position
The four defensive linemen (in red) have their hands on the ground in a "three point stance"
This defense (in white) is in a base 4–3 set. Just behind the four defensive linemen (whose hands are on the ground) are three linebackers (Nos. 55, 3 and 16), and further back are two safeties (numbers 24 and 44). The two cornerbacks are off screen to the left and right.
American football, also known as gridiron football, is a team sport played by two teams of eleven players on a rectangular field with goalposts at each end. The offense, the team with possession of the oval-shaped football, attempts to advance down the field by running with the ball or throwing it, while the defense, the team without possession of the ball, aims to stop the offense's advance and to take control of the ball for themselves. The offense must advance at least ten yards in four downs or plays; if they fail, they turn over the football to the defense, but if they succeed, they are given a new set of four downs to continue the drive. A game is won by the team with the higher number of points, which are scored primarily by advancing the ball into the opposing team's end zone for a touchdown or kicking the ball through the opponent's goalposts for a field goal.
Larry Fitzgerald (in blue) catches a pass while Cortland Finnegan (in red) plays defense at the 2009 Pro Bowl.
Walter Camp, the "Father of American Football", in 1878 when Camp was captain of Yale University's football team
The dangers associated with the sport depicted in a 1908 cartoon by William Charles Morris
Pudge Heffelfinger, widely regarded as the first professional football player