The names of commissioned ships of the United States Navy all start with USS, for United States Ship. Non-commissioned, primarily civilian-crewed vessels of the U.S. Navy under the Military Sealift Command have names that begin with USNS, standing for United States Naval Ship. A letter-based hull classification symbol is used to designate a vessel's type. The names of ships are selected by the Secretary of the Navy. The names are those of states, cities, towns, important persons, important locations, famous battles, fish, and ideals. Usually, different types of ships have names originated from different types of sources.
Modern aircraft carriers and submarines use nuclear reactors for power. See United States naval reactors for information on classification schemes and the history of nuclear-powered vessels.
