Rating system of the Royal Navy in the context of "Gun deck"

A corvette is a small warship. It is traditionally the smallest class of vessel considered to be a proper (or "rated") warship. The warship class above the corvette is that of the frigate, while the class below was historically that of the sloop-of-war.

The modern roles that a corvette fulfills include coastal patrol craft, missile boat and fast attack craft. These corvettes are typically between 500 and 2,000 tons. Recent designs of corvettes may approach 3,000 tons and include a hangar to accommodate a helicopter, having size and capabilities that overlap with smaller frigates. However unlike contemporary frigates, a modern corvette does not have sufficient endurance or seaworthiness for long voyages.

During the 18th and 19th centuries, a sloop-of-war was a warship of the Royal Navy with a single gun deck that carried up to 18 guns. The rating system of the Royal Navy covered all vessels with 20 or more guns; thus, the term encompassed all unrated warships, including gun-brigs and cutters. In technical terms, even the more specialised bomb vessels and fire ships were classed by the Royal Navy as sloops-of-war, and in practice these were employed in the role of a sloop-of-war when not carrying out their specialised functions.

In World War I and World War II, the Royal Navy reused the term "sloop" for specialised convoy-defence vessels, including the Flower class of the First World War and the highly successful Black Swan class of the Second World War, with anti-aircraft and anti-submarine capabilities. They performed similar duties to the destroyer escorts of the United States Navy, and also performed similar duties to the smaller corvettes of the Royal Navy.

In Royal Navy jargon, a man-of-war (also man-o'-war, or simply man) was a powerful warship or frigate which was frequently used in Europe from the 16th to the 19th century. Although the term never acquired a specific meaning, it was usually reserved for a sailing ship armed with cannon. The rating system of the Royal Navy classified men-of-war into six "rates", a "first-rate" having the greatest armament, and a "sixth-rate" the least.

In the rating system of the Royal Navy used to categorise sailing warships, a fifth-rate was the second-smallest class of warships in a hierarchical system of six "ratings" based on size and firepower.