ship vs vessel

ship and vessel both are nouns.

Word	Noun	Adjective	Verb	Adverb
ship	Yes	No	Yes	No
vessel	Yes	No	No	No

As nouns, vessel is a hypernym of ship; that is, vessel is a word with a broader meaning than ship:

Other hypernyms of ship include watercraft.

ship (noun)	vessel (noun)
a vessel that carries passengers or freight	a craft designed for water transportation
	an object used as a container (especially for liquids)
	a tube in which a body fluid circulates