fin keel vs centreboard

fin keel and centreboard both are nouns.

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

As nouns, centreboard is a hyponym of fin keel; that is, centreboard 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
centreboard: a retractable fin keel used on sailboats to prevent drifting to leeward

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

fin keel (noun)	centreboard (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