Dreadnoughts (DN): These are usually massive ships with a design goal to pulverize Battleships or destroy small fleets. Typically not mass produced.
Battleships (BB): Battleships are typically the largest mass produced ships fielded by a space navy. These ships are designed to be able to drop cruisers or harass small fleets of destroyers and below. They also usually lack non-military functions.
Battle Cruisers (BC): An intermediate stage between Cruisers and Battleships. They are cruisers who focus on combat over other tasks.
Cruisers (CR): Cruisers make up the majority of most capitol ships used providing a balance point between Battleships and smaller vessels such as Corvettes. Cruisers typically must support a variety of roles from exploration to combat and everything in-between.
Frigates (FG): These are the smallest ships generally capable of holding bays for small craft. They hold the place between full sized Cruisers and Corvettes. The smallest of these may be capable of planetary landings and launches.
Corvettes (CV): The smallest of all capitol ships these cannot hold bays for small craft. They can however have mountings for transporting small craft along their hulls. Most Corvettes are capable of planetary landings.
Shuttles/Gunboats (SH/GB): Largest small craft these are designed to move between planets and other objects in space. Gunboats are shuttle sized small craft geared for combat whereas shuttles are geared for cargo. Some Shuttle or Gunboats overlap Corvettes in function and purpose.
Fighters (LF/F/HF): Fighters are typically one or two person small craft that aren’t designed with much, if any, cargo space. They usually rely on larger vessels to move them from place to place due to limited range.
Carriers (CA): Carriers are designed to carrier fighters over other possible equipment and provide command and control for small craft. Carriers come in several different types and sizes from cruiser sized to Dreadnought size.
Monitor: Monitors are cruiser and up size-wise vessels that have limited movement. In all cases these vessels are not designed for exo-solar travel. Other than that though, while most have fairly small drive to mass ratios some are actually rather quick. Satellites of sufficient size can be classed as Monitors. Monitors are abbreviated as ‘M’ and then added to their designation, such as: MCA, MCR, MBC, MBB, or MDN.
Destroyer: Destroyers are typically Frigates, though sometimes corvettes, that are geared for
combat. Destroyers are a rare exception as they are assumed to be Frigates. So rather than classing a ship as ‘FG’, Destroyer frigates tends to be classes as ‘DD’. However they can be classed as ‘DFG’ as well to add to the confusion. Destroyer Corvettes are labeled as ‘DCV’.
Heavy: Heavy vessels are usually larger than average in mass for their type. This is designated by a ‘H’ label. ‘CA’ and ‘CR’ are the two classes that commonly get this treatment and become ‘HCA’ and ‘HCR’. However it has happened where something gets designated as a ‘HFG’, though this could be a ‘LCR’ as well, or a ‘HBB’ which usually is a ‘DN’.
Light: Light is the opposite of heavy, something that is under-massed for its type. This gets abbreviated with ‘L’. Usually with the same issues and considerations as heavy, but in reverse. Light BB’s would actually imply that it is a BC.
Escort: Escort is the designation for a variety of vessels designed to function from within a fleet. The most common type however to get this designation on carriers, making ECA a common abbreviation. Often however they are even more complex such as ‘ELCA’ or ‘EHCA’, implying both size and purepose.
General Adjectives: Other Adjectives are applied to ship types as well, such as: Assault, Explorer, Survey, Science, Landing, etc. These describe the typical or primary function of the vessel rather than its type. However usually they aren’t abbreviated, so an ‘Assault cruiser’ would abbreviate as CR and ignore the ‘assault’ part.