To officiate means to serve in an official role at an event, ceremony, or competition. When someone officiates, they're in charge of making sure everything follows the proper rules and procedures.

Referees and umpires officiate sports games: they watch for rule violations, make calls, and keep the game fair. A referee officiating a soccer match blows the whistle when someone commits a foul. An umpire officiating a baseball game calls balls and strikes.

Religious leaders and judges also officiate. A minister might officiate a wedding ceremony, meaning she leads the service and legally declares the couple married. A judge might officiate in a courtroom, directing the proceedings and making rulings on the law.

When you officiate, you're performing an important duty that requires knowledge, authority, and fairness. Teachers sometimes ask students to officiate class debates or competitions, giving them practice in being fair and following rules even when friends are involved. An official (the noun) is someone who officiates: a game official, a government official, or a school official all have authority and responsibilities in their particular roles.