A ship prefix is a combination of letters, usually abbreviations, used in front of the name of a civilian or naval ship that has historically served numerous purposes, such as identifying the vessel's mode of propulsion, purpose, or ownership/nationality. In the modern environment, prefixes are cited inconsistently in civilian service, whereas in government service a vessel's prefix is seldom omitted due to government regulations dictating that a certain prefix be used. Today the common practice is to use a single prefix for all warships of a nation's navy, and other prefixes for auxiliaries and ships of allied services, such as coast guards. For example, the modern navy of Japan adopts the prefix "JS" – Japanese Ship, or the US navy has adopted the USS prefix. However, not all navies use prefixes. Among the blue-water navies, those of France, Brazil, China, Russia, Germany, Ukraine, and Spain do not use ship prefixes. NATO designations such as FS, FGS, and SPS can be used if needed.