Basketball games of every level begin with a jump ball to decide initial possession. Two players stand opposite each other, the referee tosses the ball between them and the team that grabs the ball first goes on offense. After that, each level has different rules to decide which team should get possession of the ball if there is a subsequent jump ball or held ball situation, and at the beginning of subsequent play periods.
There is a jump ball at the beginning of the game only, with the team winning the jump ball gaining possession. Afterward, teams alternate getting the ball on any held ball or jump ball situation. This alternation includes the beginning of subsequent periods. The team that did not win the first jump ball is the first to get the ball on alternating possessions.
For example, team A wins the jump ball at the beginning of the game. There are no held ball or jump ball situations throughout the first half of play. Team B would automatically get the ball at the start of the second half. If, however, there is a held/jump ball during the half, team B would gain possession and play would continue. If there is not another such situation, team A would get the ball at the start of the second half.
There is a 24-second shot clock in international play. If the offensive team is awarded the ball on alternating possession, the shot clock continues to count down from the point at which the game was stopped. If the defense gains the ball, the clock is reset to 24 seconds.
NBA and WNBA
The first quarter, third quarter, and overtime periods begin with a jump ball. The losers of the jump ball gain possession of the ball at the starts of the second and fourth quarters. All held ball and jump ball situations throughout the game are decided by jump balls.
If the offensive team wins the jump ball, the clock is set to 14 seconds, if there were 14 seconds or fewer on the clock when time was stopped, or the clock continues to run if there were more than 14 seconds. If the defense wins the jump, the shot clock is reset to 24 seconds.
Games and overtimes begin with a jump ball and teams alternate possession from that point on, as in international play. College basketball is played in two halves, so the team that was awarded possession of the ball most recently forfeits possession to its opponent at the start of the second half.
The 35-second shot clock in men's games and 30-second shot clock in women's games is reset if the team on defense is awarded the ball. If the offensive team retains possession, the clock continues from the point at which it was stopped.