Very good question kem eng. The definition of ships has been changing along with the ships from the time of sail ships to modern nuclear powered air craft carriers.
For example in the days of sail ships a Frigate was a ship which carried all its guns on one deck instead of others which carried different sized guns on different levels.
Well in modern times the surface fleet consists of four main types of ship classes (excluding Air Craft Carriers of course
).
They are Cruisers, Destroyers, Frigates and Corvettes.
Although each class has a number of sub-classes but I will only explain the basics here.
Different countries maybe using different classifications for ships so the definitions here correspond to the ones used by the United States Navy.
Cruisers:
In military terminology, a cruiser is a large warship capable of engaging multiple targets simultaneously.
Modern United States Navy guided missile cruisers (CG and CGN hull classification symbols) perform primarily in a Battle Force role. These ships are multi-mission -- anti-aircraft (AAW), anti-submarine (ASW), and anti-surface (ASUW) surface combatants capable of supporting carrier battle groups, amphibious forces, or of operating independently and as flagships of surface action groups.
Destroyers:
In military terminology, a destroyer is a fast and maneuverable yet long-endurance vehicle intended to escort larger vessels in a fleet or battle group and defend them against smaller, short-range attackers.
Frigates:
In modern military terminology, a frigate is a warship intended to protect other warships and merchant ships as anti-submarine warfare (ASW) combatants for amphibious expeditionary forces, underway replenishment groups, and merchant convoys.
Corvette:
A corvette is a small, maneuverable, lightly armed warship, smaller than a frigate.
When referring to sailing ships, a corvette is a ship-rigged sloop.
Almost all modern navies use ships smaller than frigates for coastal duty, but not all of them use the term "corvette."
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