A penalty against the team in possession of the ball when the shot clock reaches zero. The penalty results in a turnover (change of possession to the other team).
The official time period of the shot clock in the NBA is 24 seconds. First introduced in 1954, the shot clock changed the way the game was played, as it prevented teams that were ahead from killing the clock with nearly endless passing of the basketball.
The 24 second violation is the enforcement of the shot clock limit. It occurs when a team has failed to make a shot that touches the rim of the basket within the allotted 24 seconds of the shot clock. A buzzer sounds and the backboard lights up-the penalty is ruled a turnover, and the defensive team gains possession of the ball.