linguistic:voice_change
Defensive unit

The role of the defense is to prevent the offense from scoring by tackling the ball carrier or by forcing turnovers. Turnovers include interceptions (a defender catching a forward pass intended for the offense) and forced fumbles (taking possession of the ball from the ballcarrier).

The defensive line (DL) consists of defensive ends (DE) and defensive tackles (DT). Defensive ends line up on the ends of the line, while defensive tackles line up inside, between the defensive ends. The primary responsibilities of defensive ends and defensive tackles are to stop running plays on the outside and inside, respectively, to pressure the quarterback on passing plays, and to occupy the line so that the linebackers can break through.

Linebackers line up behind the defensive line but in front of the defensive backfield. They are divided into two types: middle linebackers (MLB) and outside linebackers (OLB). Linebackers tend to serve as the defensive leaders and call the defensive plays, given their vantage point of the offensive backfield. Their roles include defending the run, pressuring the quarterback, and tackling backs, wide receivers, and tight ends in the passing game.

The defensive backfield, often called the secondary, consists of cornerbacks (CB) and safeties (S). Safeties are themselves divided into free safeties (FS) and strong safeties (SS). Cornerbacks line up outside the defensive formation, typically opposite a receiver to be able to cover them. Safeties line up between the cornerbacks but farther back in the secondary. Safeties tend to be viewed as "the last line of defense" and are responsible for stopping deep passing plays as well as breakout running plays.