Ship

A ship is a large, sea-going watercraft, sometimes with multiple decks. A ship generally has enough size to carry its own boats, such as lifeboats, dinghies, or runabouts. A rule of thumb saying goes: "a boat can fit on a ship, but a ship can't fit on a boat". Often local law and regulation will define the exact size which a boat requires to become a ship. During the age of sail, ship signified a ship-rigged vessel, that is, one with three or more masts, generally three, all square-rigged. Such a vessel would usually have one fore and aft sail on her aftermost mast which was usually the mizzen. Almost invariably she would also have a bowsprit but this was not part of the definition. The same economic pressures which increased sizes to the point of carrying four or five masts, also introduced the fore and aft rig to larger vessels, so few ship-rigged vessels were built with more than three masts. The five-masted Preussen was the outstanding example but the big German ships and barques were built partly for prestige reasons.
Nautical means connected to sailors, particularly customs and practices at sea. Naval is the adjective pertaining to ships though in common usage, it has come to be more mainly associated with the noun 'navy'.