In tennis, there are four types of officials, 3 having the name "umpire" in their title. These officials are divided into two sections: on-court and off-court officials. The on-court officials include the chair umpire and line umpire. The officials off of the court are the referee and the chief umpire. Line umpires are at the bottom of the officiating hierarchy, as they directly report to the chair umpire. The referee is above the chair umpire, and the chief umpire is at the top of the hierarchy.
The chair umpire serves the role as a general overseer during a match. They have authority over the line umpires in all scenarios, and can overrule calls if a clear mistake is made. The chair umpire has many responsibilities, with the principal goal of making sure a match runs smoothly and orderly. They must assure that all timing during a match is obeyed, and are responsible for this by use of an approved stopwatch.
Additionally, they must ensure the players and the court are properly equipped, attired, regulated, and cordial for the match prior to its start. Chair umpires must also officially keep track of and notify the players of the match score, ball inspection, and complete a final report at the conclusion of the match.
The line umpire has less responsibility than the chair umpire. The primary role of a line umpire is to pay close attention to, and have full responsibility of, their assigned line on the court during a match. Line umpires must not speak if a chair umpire overrules a call, and must not talk to, congratulate, support, or applaud any player during a match in any way. Line umpires are also responsible for accompanying a player who leaves a match for toilet or attire purposes and must ensure that they leave and return doing only that.