Rules and regulations

Measurements and time limits discussed in this section often vary among tournaments and organizations; international and NBA rules are used in this section.
The object of the game is to outscore one's opponents by throwing the ball through the opponents' basket from above while preventing the opponents from doing so on their own. An attempt to score in this way is called a shot. A successful shot is worth two points, or three points if it is taken from beyond the three-point arc which is 6.25 meters (20 ft 6 in) from the basket in international games and 23 ft 9 in (7.24 m) in NBA games.

Playing regulations
Games are played in four quarters of 10 (international) or 12 minutes (NBA). College games use two 20 minute halves while most high school games use eight minute quarters. Fifteen minutes are allowed for a half-time break, and two minutes are allowed at the other breaks. Overtime periods are five minutes long. Teams exchange baskets for the second half. The time allowed is actual playing time; the clock is stopped while the play is not active. Therefore, games generally take much longer to complete than the allotted game time, typically about two hours.
Five players from each team (out of a twelve player roster) may be on the court at one time. Substitutions are unlimited but can only be done when play is stopped. Teams also have a coach, who oversees the development and strategies of the team, and other team personnel such as assistant coaches, managers, statisticians, doctors and trainers.
For both men's and women's teams, a standard uniform consists of a pair of shorts and a jersey with a clearly visible number, unique within the team, printed on both the front and back. Players wear high-top sneakers that provide extra ankle support. Typically, team names, players' names and, outside of North America, sponsors are printed on the uniforms.
A limited number of time-outs, clock stoppages requested by a coach for a short meeting with the players, are allowed. They generally last no longer than one minute unless, for televised games, a commercial break is needed.
The game is controlled by the officials consisting of the referee ("crew chief" in the NBA), one or two umpires ("referees" in the NBA) and the table officials. For both college and the NBA there are a total of three referees on the court. The table officials are responsible for keeping track of each teams scoring, timekeeping, individual and team fouls, player substitutions, team possession arrow, and the shot clock.

Equipment

Traditional eight-panel basketball

A diagram of a FIBA basketball court.
The only essential equipment in basketball is the basketball and the court: a flat, rectangular surface with baskets at opposite ends. Competitive levels require the use of more equipment such as clocks, scoresheets, scoreboard(s), alternating possession arrows, and whistle-operated stop-clock systems.
A regulation basketball court in international games is 28 by 15 meters (approx. 92 by 49 ft) and in the NBA is 94 by 50 feet (29 by 15 m). Most courts are made of wood. A steel basket with net and backboard hang over each end of the court. At almost all levels of competition, the top of the rim is exactly 10 feet (3.05 m) above the court and 4 feet (1.2 m) inside the baseline. While variation is possible in the dimensions of the court and backboard, it is considered important for the basket to be of the correct height; a rim that is off by but a few inches can have an adverse effect on shooting.

Violations
The ball may be advanced toward the basket by being shot, passed between players, thrown, tapped, rolled or dribbled (bouncing the ball while running).
The ball must stay within the court; the last team to touch the ball before it travels out of bounds forfeits possession. The ball-handler may not move both feet without dribbling, known as traveling, nor may he dribble with both hands or catch the ball in between dribbles, a violation called double dribbling. A player's hand cannot be under the ball while dribbling; doing so is known as carrying the ball. A team, once having established ball control in the front half of the court, may not return the ball to the backcourt. The ball may not be kicked nor struck with the fist. A violation of these rules results in loss of possession, or, if committed by the defense, a reset of the shot clock.
There are limits imposed on the time taken before progressing the ball past halfway (8 seconds in international and NBA; 10 seconds in NCAA and high school), before attempting a shot (24 seconds in the NBA; 35 seconds in NCAA), holding the ball while closely guarded (5 seconds), and remaining in the restricted area (the lane, or "key") (3 seconds). These rules are designed to promote more offense. Note: most high school games do not employ a shot clock.
No player may interfere with the basket or ball on its downward flight to the basket, or while it is on the rim (or, in the NBA, while it is directly above the basket), a violation known as goaltending. If a defensive player goaltends, the attempted shot is considered to have been successful. If a teammate of the shooter goaltends, the basket is cancelled and play continues with the defensive team being given possession.

Fouls


The referee signals that a foul has been committed.
An attempt to unfairly disadvantage an opponent through physical contact is illegal and is called a foul. These are most commonly committed by defensive players; however, they can be committed by offensive players as well. Players who are fouled either receive the ball to pass inbounds again, or receive one or more free throws if they are fouled in the act of shooting, depending on whether the shot was successful. One point is awarded for making a free throw, which is attempted from a line 15 feet (4.5 m) from the basket.
The referee may use discretion in calling fouls (for example, by considering whether an unfair advantage was gained), sometimes making fouls controversial calls. The calling of fouls can vary between games, leagues and even between referees.
A player or coach who shows poor sportsmanship, for instance, by arguing with a referee or by fighting with another player, can be charged with a more serious foul called a technical foul. The penalty involves free throws (which unlike a personal foul, the other team can choose who they want to shoot the free throws) and varies between leagues. Repeated incidents can result in disqualification. Blatant fouls with excessive contact or that are not an attempt to play the ball are called unsportsmanlike fouls (or flagrant fouls in the NBA) and typically will result in ejection.
If a team surpasses a preset limit of team fouls in a given period (quarter or half) – four for NBA and international games – the opposing team is awarded one or two free throws on all subsequent fouls for that period, the number depending on the league. In the US college game if a team surpasses 7 fouls in the half the opposing team is awarded a one-and-one free throw (make the first you have a chance at a second). If a team surpasses 10 fouls in the half the opposing team is awarded two free throws on all subsequent fouls for the half. A player who commits five fouls, including technical fouls, in one game (six in some professional leagues, including the NBA) is not allowed to participate for the rest of the game, and is described as having "fouled out".
After a team has committed a specified number of fouls, it is said to be "in the penalty". On scoreboards, this is usually signified with an indicator light reading "Bonus" or "Penalty" with an illuminated directional arrow indicating that team is to receive free throws when fouled by the opposing team. (Some scoreboards also indicate the number of fouls committed.)
The number of free throws awarded increases with the number of fouls committed. Initially, one shot is awarded, but after a certain number of additional fouls are committed the opposing team may receive (a) one shot with a chance for a second shot if the first shot is made, called shooting "one-and-one", or (b) two shots. If a team misses the first shot (or "front end") of a one-and-one situation, the opposing team may reclaim possession of the ball and continue play. If a team misses the first shot of a two-shot situation, the opposing team must wait for the completion of the second shot before attempting to reclaim possession of the ball and continuing play.
If a player is fouled while attempting a shot and the shot is unsuccessful, the player is awarded a number of free throws equal to the value of the attempted shot. A player fouled while attempting a regular two-point shot, then, receives two shots. A player fouled while attempting a three-point shot, on the other hand, receives three shots.
If a player is fouled while attempting a shot and the shot is successful, typically the player will be awarded one additional free throw for one point. In combination with a regular shot, this is called a "three-point play" because of the basket made at the time of the foul (2 points) and the additional free throw (1 point). Four-point plays, while rare, can also occur.