small boat vs dory

small boat and dory both are nouns.

Word	Noun	Adjective	Verb	Adverb
small boat	Yes	No	No	No
dory	Yes	No	No	No

As nouns, dory is a hyponym of small boat; that is, dory is a word with a more specific, narrower meaning than small boat:

small boat: a boat that is small
dory: a small boat of shallow draft with cross thwarts for seats and rowlocks for oars with which it is propelled

Other hyponyms of small boat include canoe, cockleshell, coracle, dinghy, rowboat, gig, racing boat, skiff, yawl.

small boat (noun)	dory (noun)
a boat that is small	marine fishes widely distributed in mid-waters and deep slope waters
	pike-like freshwater perches
	a small boat of shallow draft with cross thwarts for seats and rowlocks for oars with which it is propelled