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 (by the International Olympic Committee). Referees may be assisted by umpires, linesmen, timekeepers, touch judges, or video review officials.
Football (association)
Originally team captains would consult each other in order to resolve any dispute on the pitch. Eventually this role was delegated to an umpire. Each team would bring their own partisan umpire allowing the team captains to concentrate on the game. Later, the referee, a third "neutral" official was added; this referee would be "referred to" if the umpires could not resolve a dispute. The referee did not take his place on the pitch until 1891, when the umpires became linesmen (now assistant referees). Today, in many amateur football matches, each side will still supply their own partisan assistant referees (still commonly called club linesmen) to assist the neutral referee appointed by the governing football association if one or both assistant referees are not provided. In this case, the role of the linesmen is limited to indicating out of play and cannot decide off side.
An association football (soccer) match is presided over by a referee, whom the Laws of the Game give "full authority to enforce the Laws of the Game in connection with the match to which he has been appointed" (Law 5). The referee is oftentimes assisted by two assistant referees, and sometimes by a fourth official.
Rugby
In 1892, the International Rugby Board was created as a result of a disputed try that the captains could not agree on whether it had been scored. The rugby laws were changed to require one referee and two touch judges at each game to make the arbitration easier and more consistent.
Football (American and Canadian)
An American football (or Canadian football) referee is responsible for the general supervision of the game and has the final authority on all rulings. The referee is assisted by up to six other officials on the field. These officials are commonly referred to as "referees" but each has a title based on position and responsibilities during the game: referee, head linesman ("down judge" in the NFL), line judge, umpire, back judge, side judge, and field judge. In the modern XFL, an additional "ball judge", who wears a red hat, is on the field, but does not have the power to call penalties.
Football (Gaelic)
There are usually 7 officials in Gaelic football. A main referee follows the play around the field and has the final authority on decisions such as fouls, throws and card-issuing, un-disputable by players. The main play referee is assisted by two linesmen, who make decisions on who gains possession when the ball goes out of the field of play, and can also advise the referee on off-the-ball events such as a fight or an illegal tackle. As well as the referee and two linesmen, there are two umpires at each end of the field of play who stand on either side of the goal post and raise a white flag for a point, or a green flag for a goal respectively, also calling wides and square-balls. An umpire can also advise the referee on off-the-ball incidents, but does not hold as much authority as a linesman. In recent times, technology called 'Hawk-eye' can be used if both the umpires and referee are unsure of whether a point has been scored or not, though this technology is not widely available.
Bandy
A game of bandy is officiated by a referee, the authority and enforcer of the rules, whose decisions are final. The referee may be assisted by one or two assistant referees.
Basketball
In international basketball and in college basketball, the referee is the lead official in a game, and is assisted by either one or two umpires. In the National Basketball Association, the lead official is referred to by the term crew chief and the two other officials are the referee and umpire. All of the officials in a basketball game are generally accepted to have the same authority as the lead official and therefore they are collectively known as the officials or referees.
Boxing
In boxing a referee is the person who enforces the rules during the fight. He gives instructions to the fighters, starts and stops the count when a competitor is down, and makes the determination to stop a fight when a competitor cannot continue without endangering his health.