A navy (or maritime force) is a fleet of waterborne military vessels (watercraft) and its associated naval aviation, both sea-based and land-based. It is the branch of a nation's armed forces principally designated for naval and amphibious warfare; namely, lake-borne, riverine, littoral, or ocean-borne combat operations and related functions. It includes anything conducted by surface ships, amphibious ships, submarines, and seaborne aviation, as well as ancillary support, communications, training, and other fields; recent developments have included space-related operations. The strategic offensive role of a navy is projection of force into areas beyond a country's shores (for example, to protect sea-lanes, ferry troops, or attack other navies, ports, or shore installations). The strategic defensive purpose of a navy is to frustrate seaborne projection-of-force by enemies. The strategic task of the navy also may incorporate nuclear deterrence by use of nuclear missiles. Naval operations can be broadly divided between riverine and littoral applications (brown-water navy) and open-ocean applications (blue-water navy), although the distinction is more about strategic scope than tactical or operational division.
In most nations, the term "naval", as opposed to "navy", is interpreted as encompassing all maritime military forces, e.g., navy, marine / marine corps, and coast guard forces.
Etymology and senses
First attested in English in the early 14th century, the word "navy" came via Old French navie, "fleet of ships", from the Latin navigium, "a vessel, a ship, bark, boat", from navis, "ship". The word "naval" came from Latin navalis, "pertaining to ship"; cf. Greek ναῦς (naus), "ship", ναύτης (nautes), "seaman, sailor". The earliest attested form of the word is in the Mycenaean Greek compond word ????, na-u-do-mo (*naudomoi), "shipbuilders", written in Linear B syllabic script.[n 1] There is also a possible connection to the Sanskrit word Nava for boat/ship.The word formerly denoted fleets of both commercial and military nature. In modern usage "navy" used alone always denotes a military fleet, although the term "merchant navy" for a commercial fleet still incorporates the non-military word sense. This overlap in word senses between commercial and military fleets grew out of the inherently dual-use nature of fleets; centuries ago