Captain is a title for the commander of a military unit, the commander of a ship, aeroplane, spacecraft, or other vessel, or the commander of a port, fire department or police department, election precinct, etc. The captain is a military rank in armies, navies, Public Health Service, coast guards, etc., typically at the level of an officer commanding a company or battalion of infantry, a ship, or a battery of artillery, or similar distinct unit. The terms also may be used as an informal or honorary title for persons in similar commanding roles.