vessel vs sailing ship

vessel and sailing ship both are nouns.

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

As nouns, sailing ship is a hyponym of vessel; that is, sailing ship is a word with a more specific, narrower meaning than vessel:

vessel: a craft designed for water transportation
sailing ship: a vessel that is powered by the wind; often having several masts

vessel (noun)	sailing ship (noun)
a craft designed for water transportation	a vessel that is powered by the wind; often having several masts
an object used as a container (especially for liquids)
a tube in which a body fluid circulates