sloop vs sailing vessel

sloop and sailing vessel both are nouns.

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

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

sloop: a sailing vessel with a single mast set about one third of the boat's length aft of the bow
sailing vessel: a vessel that is powered by the wind; often having several masts

Other hypernyms of sloop include sailing ship.

sloop (noun)	sailing vessel (noun)
a sailing vessel with a single mast set about one third of the boat's length aft of the bow	a vessel that is powered by the wind; often having several masts