The names of commissioned ships of the U.S. Navy are prefixed with the letters "USS", designating "United States Ship". Non-commissioned, civilian-manned vessels of the navy have names that begin with "USNS", standing for "United States Naval Ship". The names of ships are officially selected by the secretary of the navy, often to honor important people or places. Additionally, each ship is given a letter-based hull classification symbol (for example, CVN or DDG) to indicate the vessel's type and number. All ships in the navy inventory are placed in the Naval Vessel Register, which is part of "the Navy List" (required by article 29 of the United Nations Convention on the Law of the Sea). The register tracks data such as the current status of a ship, the date of its commissioning, and the date of its decommissioning. Vessels that are removed from the register prior to disposal are said to be stricken from the register. The navy also maintains a reserve fleet of inactive vessels that are maintained for reactivation in times of need.
The U.S. Navy was one of the first to install nuclear reactors aboard naval vessels; today, nuclear energy powers all active U.S. aircraft carriers and submarines. In the case of the Nimitz-class carrier, two naval reactors give the ship almost unlimited range and provide enough electrical energy to power a city of 100,000 people. The U.S. Navy previously operated nuclear-powered cruisers, but all have been decommissioned.
In the early 2010, the U.S. Navy had identified a need for 313 combat ships, but could only afford 232 to 243 ships. In March 2014, the Navy started counting self-deployable support ships such as minesweepers, surveillance craft, and tugs in the "battle fleet" in order to reach a count of 272 as of October 2016, and it includes ships that have been put in "shrink wrap".The number of ships generally ranged between 270 and 300 throughout the late 2010s. As of February 2022, the Navy has 296 battle force ships, however analyses state the Navy needs a fleet of more than 500 in order to meet its commitments.