Starship classification

Unofficially, many starships are classified by their design type. Although Starfleet tries not to classify their vessels in any such categorization, there has been numerous occasions where a Starfleet officer referred to another Starfleet vessel by its type or when refering to enemy vessels during a fleet engagement, such as in Operation Return, when Captain Sisko calls upon Galaxy wings to engage Galor class destroyers. (DS9: "Favor the Bold")

Primary ships

 * Explorer
 * Dreadnought
 * Battleship
 * Cruisers
 * Light cruiser
 * Medium cruiser
 * Heavy cruiser
 * Tactical cruiser
 * Battle cruiser
 * Destroyer
 * Escort
 * Frigate
 * Interceptor
 * Attack fighter

Support ships

 * Auxiliary craft
 * Escape pod
 * Runabout
 * Shuttlecraft
 * Shuttlepod
 * Cargo drone
 * Courier
 * Freighter
 * Raider
 * Science vessel
 * Scout
 * Surveyor
 * Supply ship
 * Tanker
 * Transport
 * Tug

Other designations

 * Warbird
 * Bird of Prey

Background
In some unclear terms, the designations for several starship classes has been the issue of some confusion. Some examples are as below:
 * The Oberth class has sometimes been confused with the scout designation, though it is officially a science vessel rather than a scout.
 * Similarly, the Constitution class starship has been classified in multiple categories as well, most notably as a heavy cruiser (and as a battlecruiser by the Klingons).
 * The Constitution class has also had some confusion. It may have been a new kind of heavy cruiser in its early life, then later called a medium cruiser, light cruiser, and possibly even a destroyer in its late life. Another possibility was being classified as an explorer, which is similar to a heavy cruiser. If this is still its unofficial designation, then it would contradict its current status. Thus the confusion.
 * The Galaxy class was called an explorer, then later a heavy cruiser, then a battlecruiser. An alternate timeline version of Captain Jean-Luc Picard referred to his Galaxy class Enterprise-D as a "battleship" (TNG: "Yesterday's Enterprise"). What its true status is at this time is a probably cause for debate.