One answer is that a ship can carry a boat, but a boat cannot carry a ship.Another is that a ship's captain gets annoyed if you refer to his vessel as a boat, but a boat's captain does not get annoyed if you refer to his vessel as a ship.There are two explanations given for this, the first is "A boat is a craft that can be hoisted aboard a ship"; as early submarines could.
(My answer doesn't account for the naming of most vessels of the Royal Navy "HMS", although this is a relatively modern convention; the RN used to refer to "His/Her Majesty's Sloop So-and-so" and "His/Her Majesty's Frigate Such-and-such".
The Royal yacht Britannia, now moored at Leith, is "HMY".) Taken from "It's common lore that a ship rolls outboard in a turn while a boat rolls inboard.
I don't think whether one fits into another has anything to do with it" There is a more technical definition: "On a boat the centre of gravity is below the freeboard, on a ship it is above.
In practice this means a boat, such as a submarine, will lean into a curve when turning while a ship will lean out." "The difference between a ship and a boat is which way they heel or skid, when turning.
Simplistically, a ship can carry a boat, but a boat cannot carry a ship. The ship carrying a boat thing works a bit but not for a fishing boat, for example.
A ship is generally an ocean going vessel but then that doesn't work for submarines which are always boats. A sailing ship is one that has 3 or more masts with yards crossing them - but i don't suppose that helps much!" None of the forgegoing answers account for the fact that a "skiff" (a small boat) is etymologically the same as "ship", and can be hoisted aboard many larger vessels.The precise (and pedantic) definition of a ship is a vessel with no fewer than three masts, all of which carry square-rigged sails. Most of the vessels we would nowadays designate as "ships" are correctly "Motor Vessels".A ship will heel outward during a turn, a boat will turn inward during a turn. boat." I was led to believe that no formal qualification was needed to sail or operate a boat as in speed boat but in order to be in charge of a ship a formal captains creditation must be obtained and all ships must carry a bona fide qualified captain,who then has the powers to perform wedding ceremonies, sea burials and the power of imprisonment whilst on board a ship.In other terms, a motorcycle will lean inward during a turn, a car, truck, etc. it seems that these things cannot be carried out on a boat. There are different definitions, one being that a ship (sailing) must be full rigged and have a minimum of 3 masts. In general, size is what distinguishes the two, boats being smaller than ships, but the words' usage is more complicated than any one simple rule of absolute size can describe.Another is that a ship has a through fitted deck, whereas a boat has an at least partly open cockpit and may be completely open. The US Navy generally follows the "boats are smaller" rule, referring to its smaller vessels as boats and its larger ones as ships.