Twenty-one, also called 21, American, cutthroat, hustle, roughhouse or rough, is a popular variation of street

Streetball

Streetball or street basketball is a variation of the sport of basketball, typically played on outdoor courts and featuring significantly less by way of formal structure and enforcement of the game's rules...

 basketball

Basketball

Basketball is a team sport in which two teams of five players try to score points by throwing or "shooting" a ball through the top of a basketball hoop while following a set of rules...

. The game is played most often with three to five players on a half court, typically when not enough players are available to at least play three-on-three. However it is possible to play twenty-one with only two players, or more than five players. Twenty-one is an individual game that does not utilize team play.

Rules

The rules and game play are often different regionally locally – even by specific court.

Basic rules are as follow:

Typically play begins with a player shooting a free throw

Free throw

In basketball, free throws or foul shots are unopposed attempts to score points from a restricted area on the court , and are generally awarded after a foul on the shooter by the opposing team...

. If the shot is made, the player continues to shoot free throws until three consecutive free throws are made or the player misses before three are made. The free throws count as one point. If the free throw is missed, the ball becomes "live" and all players are allowed to rebound the ball. During live play, all rules apply with the exception that there are no out of bounds violations nor personal fouls.

Shots made after the ball is live count two points for a player's score. After each made field goal, the player making the field goal shoots up to three free throws in a row, until he misses. All free throws count as one point towards a player's count except for the opening free throw which counts as two points. If three free throws are made in a row, the free throw shooter is handed the ball back at the top of the key and play is live again as if the free throw was missed.

The game is won by the player who accumulates exactly 21 points. If a player goes over 21 points, then player's score is reduced to 13 points and must start from there.

Variations

Common additional rules include:

• A player can attempt a 3-pointer instead of attempting three free throws.
• If a player who has 13 points misses the next shot, regardless of whether it is a free throw, then that player's points revert to 0. This is referred to as "poison points".
• Whoever wins the game must shoot a 3-pointer , and upon success receives the 3 points in the new game, does not get the free throws, but does have the ball and may shoot again.
• Players with fewer than 13 points at the end of a game keep their points into the next game (a sort of handicapping
  Handicapping
  Handicapping, in sport and games, is the practice of assigning advantage through scoring compensation or other advantage given to different contestants to equalize the chances of winning. The word also applies to the various methods by which the advantage is calculated...
  
   system for when there is a wide variation in skill between the players).
• "Tips" or "Taps" is an addition to Twenty-One. With these rules, if a player jumps up, gets a rebound in the air and makes a shot before touching the ground, the player who initially shot the ball is said to have been "tipped." In this situation, the tipper is awarded 3 points and resumes to shoot their post-goal free throws, and the one being tipped reverts to 0 if their score is under 14, otherwise they will revert to 14. If a player gets tipped 3 times, they are out of the game. All free throws in tips must at least hit the rim, or the shot must be retried. In addition, on a free throw the ball must hit the rim before the shooting player may charge the lane.
• Another variation of the Tips rule is thus: a two-handed tip knocks the original shooter's score to 0, but if his score is already 0, he or she is out of the game. Additionally, if a player makes a tip with one hand, the original shooter is automatically out and must wait for the next airball. Also, if a player is "dunk-tipped", the last player to touch the ball is automatically out and must also wait for the next airball.

Formal use

Twenty-one is frequently used in physical education

Physical education

Physical education or gymnastics is a course taken during primary and secondary education that encourages psychomotor learning in a play or movement exploration setting....

 classes and by basketball team coaches as skill development. Because only one player is on offense at any given time against several defenders, quickness and shooting skills are essential to successful play.