riposte vs repay

riposte is a noun but repay is not a noun.

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

As verbs, riposte and repay are synonyms defined as:

Other synonyms of riposte include come back, rejoin, retort, return.

riposte (noun)	repay (noun)
(fencing) a counterattack made immediately after successfully parrying the opponents lunge
a quick reply to a question or remark (especially a witty or critical one)

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