Carrier
From Halopedia, the Halo wiki
A Carrier is a general starship classification, with warships of different subclassifications within the UNSC and Covenant fleets. Such a vessel is formally defined as "a large warship carrying fighters equipped with flight decks for takeoffs and landings". There are likely multiple classes of carrier within this general designation.
The general combat role of a carrier in combat is to deploy starfighters, such as Seraphs or Longswords. They also possess weapons themselves, not just starfighters, to protect themselves in combat when their fighters are unable to defend them. In planetary occupation missions, carriers are mobile deployers of ground forces to subjugate an enemy planet, launching dropships and top-cover fighters.
The navies of the UNSC and the Covenant had different classifications of carriers. For example, the Covenant sported light carriers, Assault Carriers, and supercarriers. Assault Carriers were on the scale of five kilometers long, giving a scale of the keel length of carrier-type warships.
