repay vs retort

repay is not a noun while retort is a noun.

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

As verbs, repay and retort are synonyms defined as:

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

repay (noun)	retort (noun)
	a vessel where substances are distilled or decomposed by heat
	a quick reply to a question or remark (especially a witty or critical one)

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