A corvette is a small, maneuverable, lightly arme warship, originally smaller than a frigate and larger than a coastal patrol craft, although many recent designs resemble frigates in size and role. During the Age of Sail, corvettes were smaller than frigates and larger than sloops-of-war, usually with a single gun deck. Almost all modern navies use ships smaller than frigates for coastal duty, but not all of them use the term corvette (from the French corvair) or equivalent. The rank Corvette Captain derives from the name of this type of ship.