If a player fouls three times without making an intervening legal shot, it is a serious foul. In games scored by the rack, such as nine ball, the fouls must be in a single rack. Some games such as eight ball do not include this rule.
The referee must warn a shooter who is on two fouls when he comes to the table that he is on two fouls. Otherwise a possible third foul will be considered to be only the second.
