catechin vs tannin

catechin and tannin both are nouns.

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

As nouns, tannin is a hypernym of catechin; that is, tannin is a word with a broader meaning than catechin:

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

Other hypernyms of catechin include tannic acid.

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