tannin vs catechin

tannin and catechin both are nouns.

Word	Noun	Adjective	Verb	Adverb
tannin	Yes	No	No	No
catechin	Yes	No	No	No

As nouns, catechin is a hyponym of tannin; that is, catechin is a word with a more specific, narrower meaning than tannin:

tannin: any of various complex phenolic substances of plant origin; used in tanning and in medicine
catechin: a tannic acid that is extracted from black catechu as a white crystalline substance

Other hyponyms of tannin include cutch, kutch.

tannin (noun)	catechin (noun)
any of various complex phenolic substances of plant origin; used in tanning and in medicine	a tannic acid that is extracted from black catechu as a white crystalline substance