. Propulsion
A boat can be powered by sails, motor, or human force, whereas a ship has dedicated engines to propel them. (Ships can also be propelled by sails or other advanced propulsion technologies)
Even though all vessels operating in the high seas are referred to as ships, submersible vessels are categorically termed as ‘boats.’
This is mainly because of the fact that in the earlier centuries, submersible vessels could be hoisted on ships till they were required to be used in naval operations.
However, while talking about differences between a ship and a boat, vessels floating on the water surface is mainly considered.
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The usage of the term ‘ship’ or ‘boat’ also depends on the region it is being used in. People from several countries often refer a medium-sized fishing vessel as a boat, or a medium-sized ferry or a recreational boat as a ship. As can be seen, people have a tendency to generalise a vessel on the basis of its size.
However, it is to note that the difference between a ship and a boat depends on a number of factors as discussed above.