reply vs repay

reply is a noun but repay is not a noun.

Word	Noun	Adjective	Verb	Adverb
reply	Yes	No	Yes	No
repay	No	No	Yes	No

As verbs, repay is a hyponym of reply; that is, repay is a word with a more specific, narrower meaning than reply:

Other hyponyms of reply include call back, counter, field, sass, come back, rejoin, retort, return, riposte, bridle.

reply (noun)	repay (noun)
the speech act of continuing a conversational exchange
a statement (either spoken or written) that is made to reply to a question or request or criticism or accusation

reply (verb)	repay (verb)
react verbally	answer back
	pay back
	make repayment for or return something
	act or give recompense in recognition of someone's behavior or actions