The defensive team or defense in American football or Canadian football, is the team that begins a play from scrimmage not in possession of the ball.
Several different "defensive sets" are used. The numbers of linemen and linebackers will vary, but most sets used in American football include a line composed of defensive ends and defensive tackles and, behind the line, linebackers, cornerbacks, a strong safety and a free safety.
- defensive end - the two defensive ends play on the outside of the defensive line. Their function is to rush the passer or stop runs.
- defensive tackle - (sometimes called a defensive guard), defensive tackles are linemen who lines up inside the defensive ends. Their function is to rush the passer, and defend against running plays. A defensive tackle that lines up directly across from the ball (on the nose of the center) is often called a nose guard. Common defensive sets have from one to three defensive tackles.
- linebacker - linebackers play behind the defensive line and perform various duties depending on the situation, including rushing the passer, covering receivers, and defending against the run. Most defensive sets have between three and five linebackers.
- cornerback - the cornerbacks primarily cover the wide receivers.
- safety - the safeties are the last line of defense (farthest from the line of scrimmage), and provide help on deep pass coverage.