In basketball, a “jump ball” is a situation where the referee throws the ball into the air, and two opposing players jump to try to catch or tap it in order to gain possession for their team. It usually happens at the start of the game or after certain stoppages, such as when two players from opposing teams have possession of the ball at the same time, known as a “held ball.”
In the NBA, after the initial jump ball at the start of the game, possession changes are determined by a “alternating possession rule,” where the team that doesn’t win the jump ball gets possession at the next held ball situation.
