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In American football, a checkdown pass is when the quarterback attempts to complete a short, accurate pass, typically to a running back or tight end, as a last option when the primary option(s) as designed by the play call are covered. The term means that the quarterback has "checked down" his list of receivers. Because the quarterback does not look for the checkdown pass until after they have scanned for open receivers down the field for about 3–4 seconds, the defensive line has had time to enter the backfield and so a checkdown pass is often thrown in the face of pressure from the defensive line. Alternatively, if the quarterback is inexperienced or the defensive team has sent a blitz, with linebackers and/or defensive backs also looking to sack the quarterback, the checkdown may also turn out to be the quarterback's second or even first look. 
A screen pass and a checkdown are different, because a screen pass is designed primarily to go to the short route after drawing in pass rushers.
The shotgun formation is a formation used by the offensive team in gridiron football mainly for passing plays, although some teams use it as their base formation. Instead of the quarterback receiving the snap from center at the line of scrimmage, in the shotgun he stands farther back, often five to seven yards off the line. Sometimes the quarterback will have a back on one or both sides before the snap, while other times he will be the lone player in the backfield with everyone spread out as receivers.
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.
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.
A screen pass is a play in gridiron football consisting of a short pass to a receiver who is protected by a screen of blockers. During a screen pass, a number of things happen concurrently in order to fool the defense into thinking a long pass is being thrown, when in fact the pass is merely a short one, just beyond the defensive linemen. Screens are usually deployed against aggressive defenses that rush the passer. Because screens invite the defense to rush the quarterback, they are designed to leave fewer defensemen behind the rushers to stop the play.
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.
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.
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 American football, a zone blitz is a defensive tactic that sends additional players to rush the opposing team's quarterback, whilst also unexpectedly redirecting a supposed pass rushing player into pass coverage instead. This tactic also likely includes zone coverage.
A trick play, also known as a gadget play, gimmick play or trickeration, is a play in gridiron football that uses deception and unorthodox tactics to fool the opposing team. A trick play is often risky, offering the potential for a large gain or a touchdown if it is successful, but with the chance of a significant loss of yards or a turnover if not. Trick plays are rarely used not only because of the riskiness, but also to maintain the element of surprise for when they are used.
A halfback (HB) is an offensive position in American football, whose duties involve lining up in the backfield and carrying the ball on most rushing plays, i.e. a running back. When the principal ball carrier lines up deep in the backfield, and especially when that player is placed behind another player, as in the I formation, that player is instead referred to as a tailback.
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, historically known as a safetyman, is a position in gridiron football which is played by a member of the defense. The safeties are defensive backs who line up from ten to fifteen yards from the line of scrimmage who can play as linebackers or deep as normal safeties. There are two variations of the position in a typical American formation: the free safety (FS) and the strong safety (SS). 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, respectively. 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. As professional and college football have become more focused on the passing game, safeties have become more involved in covering the eligible pass receivers.
The triple option is an American football play used to offer several ways to move the football forward on the field of play. The triple option is based on the option run, but uses three players who might run with the ball instead of the two used in a standard option run.
In American football, a play is a close-to-the-ground plan of action or strategy used to move the ball down the field. A play begins at either the snap from the center or at kickoff. Most commonly, plays occur at the snap during a down. These plays range from basic to very intricate. Football players keep a record of these plays in a playbook.
The Veer is an option running play often associated with option offenses in American football, made famous at the collegiate level by Bill Yeoman's Houston Cougars. It is currently run primarily on the high school level, with some usage at the collegiate and the professional level where the Veer's blocking scheme has been modified as part of the zone blocking system. The Veer is an effective ball control offense that can help minimize mismatches in a game for a team. However, it can lead to turnovers with pitches and handoff option reads.
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.
Buck-lateral is an American football play or a series of plays used in the Single-wing formation. Since the Single-Wing formation lost prominence by 1950, the football play referred to as the Buck-lateral is almost gone from football's vocabulary. However, prior to this time, the buck-lateral play gave fullbacks the option to run, lateral, or hand-off the ball to another player. Running the buck-lateral required an offensive scheme that needed the fullback to possess many specialized skills, as opposed to today's fullback who mainly blocks and carries the ball infrequently.
The run and shoot offense is an offensive system for American football which emphasizes receiver motion and on-the-fly adjustments of receivers' routes in response to different defenses. It was conceived by former high school coach Glenn "Tiger" Ellison and refined and popularized by former Portland State offensive coordinator Mouse Davis.
A route is a pattern or path that a receiver in gridiron football runs to get open for a forward pass. Routes are usually run by wide receivers, running backs and tight ends, but other positions can act as a receiver given the play.