Referee

Definition: Match official that has control of the game and is generally the final authority in all decisions.

According to Law 5 in the FIFA rulebook, the referee:

• Controls the match in co-operation with the assistant referees and, where applicable, with the fourth official.
  
• Ensures that any ball used meets the requirements of Law 2. Ensures that the players’ equipment meets the requirements of Law 4.
  
• Acts as timekeeper and keeps a record of the match.
  
• Stops, suspends or terminates the match, at his discretion, for any infringements of the Laws
  
• Stops, suspends or terminates the match because of outside interference of any kind
  
• Stops the match if, in his opinion, a player is seriously injured and ensures that he is removed from the field of play. An injured player may only return to the field of play after the match has restarted
  
• Allows play to continue until the ball is out of play if a player is, in his opinion, only slightly injured
  
• Ensures that any player bleeding from a wound leaves the field of play. The player may only return on receiving a signal from the referee, who must be satisfied that the bleeding has stopped
  
• A player cannot wear clothing with blood on it
  
• Allows play to continue when the team against which an offence has been committed will benefit from such an advantage and penalises the original offence if the anticipated advantage does not ensue at that time
  
• Punishes the more serious offence when a player commits more than one offence at the same time
  
• Takes disciplinary action against players guilty of cautionable and sending-off offences. He is not obliged to take this action immediately but must do so when the ball next goes out of play
  
• Takes action against team officials who fail to conduct themselves in a responsible manner and may, at his discretion, expel them from the field of play and its immediate surrounds
  
• Acts on the advice of assistant referees regarding incidents which he has not seen
  
• Ensures that no unauthorised persons enter the field of play
  
• Restarts the match after it has been stopped
  
• Provides the appropriate authorities with a match report which includes information on any disciplinary action taken against players, and/or team officials and any other incidents which occurred before, during or after the match
  
• Most referees wear either yellow or black, but the colours and styles vary according to individual associations.

See refereeing section of FIFA rulebook.