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In American football, a dimeback is a cornerback or safety who serves as the sixth defensive back (fourth cornerback, third safety; and in some rare cases, a fourth safety) on defense.  The third cornerback or safety on defense is known as a nickelback. The dimeback position is essentially relegated to backup cornerbacks and safeties who do not play starting cornerback or safety positions. Dimebacks are usually fast players because they must be able to keep up on passing plays with 3+ wide receivers.
Dimebacks are brought into the game when the defense uses a dime formation, which uses six defensive backs rather than four or five. Usually, a dimeback replaces a linebacker in order to gain better pass defense, although some teams may substitute the extra defensive back for a defensive lineman in their dime formation.
A running back (RB) is a member of the offensive backfield in gridiron football. The primary roles of a running back are to receive handoffs from the quarterback to rush the ball, to line up as a receiver to catch the ball, and block. There are usually one or two running backs on the field for a given play, depending on the offensive formation. A running back may be a halfback, a wingback or a fullback. A running back will sometimes be called a "feature back" if he is the team's starting running back.
In gridiron football, defensive backs (DBs), also called the secondary, are the players on the defensive side of the ball who play farthest back from the line of scrimmage. They are distinguished from the other two sets of defensive players, the defensive linemen who play directly on the line of scrimmage, and the linebackers, who play in the middle of the defense, between the defensive line and the defensive backs.
A cornerback (CB) is a member of the defensive backfield or secondary in gridiron football. Cornerbacks cover receivers most of the time, but also blitz and defend against such offensive running plays as sweeps and reverses. They create turnovers through hard tackles, interceptions, and deflecting forward passes.
In gridiron football, blitzing is a tactic used by the defense to disrupt pass attempts by the offense. During a blitz, a higher than usual number of defensive players will rush the opposing quarterback, in an attempt either to tackle him or force him to hurry his pass attempt.
This is a glossary of terms used in Canadian football. The Glossary of American football article also covers many terms that are also used in the Canadian version of the game.
Strategy forms a major part of American football. Both teams plan many aspects of their plays (offense) and response to plays (defense), such as what formations they take, who they put on the field, and the roles and instructions each player are given. Throughout a game, each team adapts to the other's apparent strengths and weaknesses, trying various approaches to outmaneuver or overpower their opponent in order to win the game.
American football positions have slowly evolved over the history of the sport. From its origins in early rugby football to the modern game, the names and roles of various positions have changed greatly, some positions no longer exist, and others have been created to fill new roles.
A formation in football refers to the position players line up in before the start of a down. There are both offensive and defensive formations and there are many formations in both categories. Sometimes, formations are referred to as packages.
In sports, a starting lineup is an official list of the set of players who will participate in the event when the game begins. The players in the starting lineup are commonly referred to as starters, whereas the others are substitutes or bench players.
In American football, a nickelback is a cornerback or safety who serves as the additional defensive back in a nickel defense. A base defense consists of two cornerbacks and two safeties, making the nickelback the fifth defensive back on the field, thus tying the name of the position to the name of the North American 5-cent piece.
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 the so-called 'special teams'. Within these three separate "platoons", various positions exist depending on the jobs that the players are doing.
Safety is a position in gridiron football on the defense. The safeties are defensive backs who line up ten to fifteen yards from the line of scrimmage. There are two variations of the position: the free safety and the strong safety. Their duties depend on the defensive scheme. The defensive responsibilities of the safety and cornerback usually involve pass coverage towards the middle and sidelines of the field. While American (11-player) formations generally use two safeties, Canadian (12-player) formations generally have one safety and two defensive halfbacks, a position not used in the American game.
The prevent defense is a defensive alignment in American football that seeks to prevent the offense from completing a long pass or scoring a touchdown in a single play and seeks to run out the clock. It is used by a defense that is winning by more than a touchdown, late in the fourth quarter, or in specific situations, such as third-and-very-long if it seems clear that the offense must pass the football to gain long yardage.
In American football, the 3–4 defense is a common defensive alignment consisting of three down linemen and four linebackers. It is a called a "base defense" because it is the default defensive alignment used on "base downs". However, defenses will readily switch to other defensive alignments as circumstances change. Alternatively, some defenses use a 4–3 defense.
Zone coverage is a defense scheme in gridiron football used to protect against the pass.
In American football, a 4–3 defense is a defensive alignment consisting of four down linemen and three linebackers. It is called a "base defense" because it is the default defensive alignment used on "base downs". However, defenses will readily switch to other defensive alignments as circumstances change. Alternatively, some defenses use a 3–4 defense.
The following terms are used in American football, both conventional and indoor. Some of these terms are also in use in Canadian football; for a list of terms unique to that code, see Glossary of Canadian football.
In American football, a back is a player who plays off of the line of scrimmage. Historically, the term "back" was used to describe multiple positions on offense and defense, although more descriptive and specific position naming is now common. Thus, "back" can refer to positions including:
In American football, the dime defense is a defensive alignment that uses six defensive backs. It is usually employed in obvious passing situations. The formation usually consists of six defensive backs, usually two safeties, and four cornerbacks, and has either four down linemen and one linebacker, or three down linemen and two linebackers. This formation is used to prevent the offense from completing a medium- to long-range pass play. This may be because the offense's running game is inefficient, time is an issue, or they need a long pass for a first down. It is also used against teams whose pass-to-run ratio predominantly favors pass. The formation, however, is vulnerable to running plays as the formation is missing two linebackers, or a linebacker and a down lineman.