ZONE—A pass coverage in which the linebackers, cornerbacks and safeties have predefined areas for which they are responsible.
3-4 DEFENSE—An alignment characterized by a three-man rush line, whose primary responsibility is to tie up blockers, and four linebackers who make most of the tackles.
4-3 DEFENSE—The defense traditionally played by most NFL teams. Features a four-man rush line and three linebackers.
53 DEFENSE—A version of the 3-4 named for Miami's Bob Matheson, who wore No. 53 during the Dolphins' 17-0 Super Bowl season of 1972. Replacing a defensive lineman, Matheson became a fourth linebacker on passing downs, giving Miami an eight-man secondary.