Ship class A ship class is a group of ships of a similar design . This is distinct from a ship - type , which might reflect a similarity of tonnage or intended use . For example , the is a nuclear aircraft carrier of the . In the course of building a class of ships , design changes might be implemented . In such a case , the ships of different design might not be considered of the same class ; each variation would either be its own class , or a subclass of the original class ( see for an example ) . If ships are built of a class whose production had been discontinued , a similar distinction might be made . Ships in a class often have names linked by a common factor : e . g . s ' names all begin with T ( , , ) ; and s are named after American battles ( , , , ) . Naval ship class naming conventions . The name of a ship class is most commonly the name of the first ship commissioned or built of its design . However , other systems can be used without confusion or conflict . United States . In the United States Navy a class is always named after the lead ship , that is , the first ship of the class to be approved by the United States Congress . Due to numbering conventions the lead ship almost always has the lowest hull number of her class . ( During World War II , the award of construction contracts was not always congruent with completion , so many ships had higher hull numbers than later - class ships with lower ones . ) Europe in general . In European navies a class is named after the first ship commissioned regardless of when she was ordered or laid down . In some cases this has resulted in different class names being used in European and U . S . references ; for example , European sources record the s of the United States Navy as " " Maryland " - class " , as was commissioned before . United Kingdom . The British Royal Navy has used several methods of naming classes . In addition to the accepted European convention , some classes have been named after a common theme in the included ships ' names , e . g . , s , and some classes were implemented as an organizational tool , making traditional methods of naming inefficient . For instance , the is also known as the " A " class . Most destroyer classes were known by the initial letter used in naming the vessels , e . g . , V and W class destroyer s . Classification by letter also helped to conflate similar smaller classes of ships as in the case of the " C " - class destroyers of 1913 whose names spread across the alphabet . Since the end of the Second World War , Royal Navy ship classes have also been known by their type number ( e . g . Type 42 destroyer . ) Russia / Soviet Union . Russian ( and Soviet ) ship classes are formally named by the numbered project that designed them . That project sometimes , but not always , had a metaphorical name , and almost always had a NATO reporting name . In addition , the ships of the class would be numbered , and that number prefixed by a letter indicating the role of that type of vessel . For example , Project 641 had no other name , though NATO referred to its members as Foxtrot class submarine s . Germany . The West German Navy ( " Bundesmarine " ) used a three - digit type number for every class in service or in advanced project state . Modified versions were identified by a single letter suffix . After the reunification of Germany the German Navy ( " Deutsche Marine " ) kept the system . Informally , classes are also traditionally named after their lead ships . Indonesia . Indonesian Navy has a traditional naming for its ship . Moreover , the ship ' s type and missions can be identified by the first number on the ship ' s three - digit hull number , which is placed on the front bows and the back of the stern . The naming convention is such as : Merchant vessel class . Merchant ships are almost always classed by a classification society . These vessels are said to be " in class " when their hull , structures , machinery , and equipment conform to International Maritime Organization and MARPOL standards . Vessels " out of class " may be uninsurable and / or not permitted to sail by other agencies . A vessel ' s class may include endorsements for the type of cargo such as " oil carrier " , " bulk carrier " , " mixed carrier " etc . It may also include class notations denoting special abilities of the vessel . Examples of this include an ice class , fire fighting capability , oil recovery capability , automated machinery space capability , or other special ability .