referee

A person or authority who oversees and rules match's activities in competitive sport

A referee is an official, in a variety of sports and competition, responsible for enforcing the rules of the sport, including sportsmanship decisions such as ejection. The official tasked with this job may be known by a variety of other titles depending on the sport, including umpire, judge, arbiter (chess), commissaire, or Technical Official. Referees may be assisted by umpires, linesmen, timekeepers, or touch judges.

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