Variations and similar games

Variations of basketball are activities based on the game of basketball, using common basketball skills and equipment (primarily the ball and basket). Some variations are only superficial rules changes, while others are distinct games with varying degrees of basketball influences. Other variations include children's games, contests or activities meant to help players reinforce skills.
Wheelchair basketball is played on specially designed wheelchairs for the physically impaired. The world governing body of wheelchair basketball is the International Wheelchair Basketball Federation (IWBF). Water basketball, played in a swimming pool, merges basketball and water polo rules. Beach basketball is played in a circular court with no backboard on the goal, no out-of-bounds rule with the ball movement to be done via passes or 2 1/2 steps, as dribbling is not allowed.
There are many variations as well played in informal settings without referees or strict rules. Perhaps the single most common variation is the half court game. Only one basket is used, and the ball must be "cleared" - passed or dribbled outside the half-court or three-point line - each time possession of the ball changes from one team to the other. Half-court games require less cardiovascular stamina, since players need not run back and forth a full court. Half-court games also raise the number of players that can use a court, an important benefit when many players want to play.
A popular version of the half-court game is 21. Two-point shots count as two points and shots from behind the three-point line count three. A player who makes a basket is awarded up to three extra free throws (or unlimited if you are playing "all day"), worth the usual one point. When a shot is missed, if one of the other players tips the ball in with two while it is in the air, the score of the player who missed the shot goes back to zero, or if they have surpassed 13, their score goes back to 13. This is called a "tip". If a missed shot is "tipped" in, but the player who tips it in only uses one hand, then the player who shot it is out of the game and has to catch an air ball to get back in. The first player to reach exactly 21 points wins. If they go over, their score goes back to 13. Jonathan
Other variations include streetball, knockout, and one-on-one; a variation in which two players will use only a small section of the court (often no more than a half of a court) and compete to play the ball into a single hoop. Such games tend to emphasize individual dribbling and ball stealing skills over shooting and team play.