Assistant referee (association football)
In association football, an assistant referee, formerly known as a linesman, helps the main referee enforce the rules of the game during a match. While the rules don't require assistant referees, most organized football matches have a team of at least two officials, including the main referee and assistant referees. Assistant referees have specific roles, such as determining when the ball goes out of play, deciding if there's an offside, and letting the referee know about rule violations the referee might have missed. They usually stand along the sidelines on opposite sides of the field.