A crew comprises a boy or a class of people who work at a common activity, generally in a structured or hierarchical organization. The word has particular nautical resonances: the tasks involved in operating a ship, particularly a sailing ship, providing numerous specialities within a ship's crew, often organised with a chain of command. Traditional nautical usage strongly distinguishes officers from crew, though the two groups combined form the ship's company. Members of a crew are often referred to by the title "Crew member".