A Substitute in basketball is a player who enters the game to replace any player on his team on the court.
This action is termed as a substitution and is only permitted when there is a stoppage of play. Substitution in basketball, just like in ice hockey and American football, is unlimited.
Substitute players are not part of the starting lineup. They are also called Bench Players, Reserves, or Backup Players. Later in the game, the substitute player may also be substituted for another.