Classification system of the UNSC Navy

Like the sea-going navies that preceded it, the UNSC Navy makes use of a classification system for its warships, providing an easy, at a glance system to compare relative ship strengths without having to get bogged down in the details of tonnage and gun diameters. Similar to a system used by the Old Earth Royal Navy, the UNSC Navy divides its ships into two broad categories; "Ships of the line" and "Non-rates".

Ships of the line
Ships of the line are so named because they are designed to take part in the naval tactic known as the line of battle, in which two columns of opposing warships will manoeuvre to bring the greatest weight of guns or missiles to bear. Since these engagements are almost invariably won by the heaviest ships carrying the most powerful guns, the natural progression is to build vessels that are the largest and most powerful of the time.

Capital ships
The capital ships of the navy are its most important warships; the ones with the heaviest firepower and armor. A capital ship is generally a leading or a primary ship in a fleet. They include Supercarriers, Carriers, and after the War of Vengeance, Battleships and Battlecruisers.

Supercarriers
Supercarriers are the largest vessels of any space-going navy. Originally an unofficial term used to describe the largest type of aircraft carrier, the term has become an official designation for any starfighter-carrying warship in excess of four kilometres in length. Because of their size and expense, even the UNSC can only maintain a few of these ships and given their vulnerability to conventional and asymmetrical threats, more and smaller carriers have been suggested over the years, such as the Musashi-class Carrier and the Stalingrad-class Carrier. However supercarriers are considered to be more cost effective than smaller carriers

An example is the Trafalgar-class Supercarrier

Escort warships
So named because of their role in escorting larger capital ships, escort warships are usually considerably smaller and cheaper than capital ships. They provide screening from missiles or plasma torpedoes, scouting duties, and add to the capital ships' firepower, often considerably.

Non-rates
So named beacuse they do not sit in the line of battle, these vessels support the fleet in operations, and include troop transports, convoy escorts, and Prowlers.

Combatants
In contrast to support starships, which are logistics vessels, combatants are designed to deliberately engage a similarly-designed enemy ship in combat and expect victory.

Support starships
Support starships are logistics vessels which transport food, fuel, and munitions to resupply the fleet. Originally, there were many different types of support ship, but most modern designs occupy all three transport roles. The weapons of support ships are purely defensive.