sailing boat vs sailing ship

sailing boat and sailing ship both are nouns.

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

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

sailing boat: a small sailing vessel; usually with a single mast
sailing ship: a vessel that is powered by the wind; often having several masts

Other hypernyms of sailing boat include sailing vessel.

sailing boat (noun)	sailing ship (noun)
a small sailing vessel; usually with a single mast	a vessel that is powered by the wind; often having several masts