repay vs refund

repay is not a noun while refund is a noun.

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

As verbs, repay and refund are synonyms defined as:

Other synonyms of repay include give back, return.

repay (noun)	refund (noun)
	the act of returning money received previously
	money returned to a payer

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