biscuit vs wafer

biscuit and wafer both are nouns.

Word	Noun	Adjective	Verb	Adverb
biscuit	Yes	No	No	No
wafer	Yes	No	No	No

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

biscuit (noun)	wafer (noun)
small round bread leavened with baking-powder or soda	a small thin crisp cake or cookie
any of various small flat sweet cakes	thin disk of unleavened bread used in a religious service (especially in the celebration of the Eucharist)
	a small adhesive disk of paste; used to seal letters