rowboat vs small boat

rowboat and small boat both are nouns.

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

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

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

rowboat (noun)	small boat (noun)
a small boat of shallow draft with cross thwarts for seats and rowlocks for oars with which it is propelled	a boat that is small