fin keel vs drop keel

fin keel and drop keel both are nouns.

Word	Noun	Adjective	Verb	Adverb
fin keel	Yes	No	No	No
drop keel	Yes	No	No	No

As nouns, drop keel is a hyponym of fin keel; that is, drop keel is a word with a more specific, narrower meaning than fin keel:

fin keel: a metal plate projecting from the keel of a shallow vessel to give it greater lateral stability
drop keel: a retractable fin keel used on sailboats to prevent drifting to leeward

Other hyponyms of fin keel include centerboard, centreboard, sliding keel.

fin keel (noun)	drop keel (noun)
a metal plate projecting from the keel of a shallow vessel to give it greater lateral stability	a retractable fin keel used on sailboats to prevent drifting to leeward