Originally, a vessel of the Mediterranean propelled by sails and by oars. The French, about 1650, transferred the name to larger vessels, and by 1750 it had been appropriated for a class of war vessels intermediate between corvettes and ships of the line. Frigates, from about 1750 to 1850, had one full battery deck and, often, a spar deck with a lighter battery. They carried sometimes as many as fifty guns. After the application of steam to navigation steam frigates of largely increased size and power were built, and formed the main part of the navies of the world till about 1870, when the introduction of ironclads superseded them.
Escort vessel designed to provide air, surface and undersea defence to naval forces and convoys. It is capable, if required, of conducting sustained independent operations to achieve a variety of missions.