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.

Unlike the offensive team, there are no formally defined defensive positions. A defensive player may line up anywhere on his side of the line of scrimmage and perform any legal action. However, most sets used in American football include a line composed of defensive ends and defensive tackles and, behind the line, linebackers, cornerbacks, and safeties.

Defensive ends and tackles are collectively called defensive line, while the cornerbacks and safeties are collectively called the secondary, or defensive backs.

• defensive end (DE) - the two defensive ends play on opposite outside edges of the defensive line. Their function is to rush and / or attack the passer, or stop offensive runs to the outer edges of the line of scrimmage. The faster of the two is usually placed on the right because this is a right-handed quarterback's blind side.
• defensive tackle (DT) - (sometimes called a defensive guard), defensive tackles are side-by-side linemen who are 'sandwiched' between the defensive ends. Their function is to rush the passer (if they can shove past the offensive linemen blocking them), and stop running plays directed at the middle of the line of scrimmage. A defensive tackle that lines up directly across from the ball (and therefore, is almost nose-to-nose with the offense's center) is often called a nose tackle or nose guard. Common defensive sets have from one to three defensive tackles.
• linebacker (LB; more specifically, OLB, MLB, LOLB, ROLB ) - 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 two and four linebackers. Linebackers are usually divided into three types: strongside (Left- or Right- Outside Linebacker: LOLB or ROLB); middle (MLB); and weakside (LOLB or ROLB). The strongside linebacker usually lines up across from the offense's tight end; he is usually the strongest LB because he must be able to shed lead blockers quickly enough to tackle the running back. The middle linebacker must correctly identify the offense's formations and what adjustments the entire defense must make, all in the fleeting seconds before the offense starts play (by snapping the ball to the quarterback). Because of this, the middle linebacker is nicknamed the 'quarterback of the defense'. The weakside linebacker is usually the most athletic or fastest linebacker, because he usually must defend an open field.
• cornerback (CB) -- (typically) two players that primarily cover the wide receivers; they attempt to prevent successful quarterback passes by either swatting the airborne ball away from the receiver, or by catching the pass themselves (automatically switching possession of the ball to their team) -- an interception. In rushing situations, their job is to contain the rusher.
• safety (FS or SS) -- the safeties are the last line of defense (farthest from the line of scrimmage), and usually help the corners with deep-pass coverage. The strong safety (SS) is usually the larger and stronger of the two, providing extra protection against run plays by standing somewhere between the free safety and the line of scrimmage. The free safety (FS) is usually the smaller and faster of the two, providing variable and extra pass protection. However, more recently, teams are looking for hybrid safeties who can do both jobs, as in a cover 2 defence, the strong safety has a greater role to play in coverage.
• nickel- and dime- backs -- in certain formations one extra (i.e., a fifth) defensive back (called a 'nickel' defense: a nickel coin = five cents) -- or even two extra (a fifth and sixth) DBs (called a 'dime' package: a dime = two nickels) -- may be used to augment the backfield and / or defensive line. Nickelbacks and dimebacks are usually used to defend pass plays with extra receivers, but they can also be used to rush quarterbacks or runningbacks more quickly than linemen or most linebackers can. A starting cornerback who is good at blitzing and tackling will sometimes be referred to as a nickleback, to distinguish them from cornerbacks who are better in coverage and poor in this respect.

See also

• American football strategy
• American football defensive schemes
• Lineman (football)
• Defensive back
• Offensive team
• Special teams
• Glossary of American football

American football terminology | Canadian football terminology

Defensive line