pay vs prepay

pay is a noun but prepay is not a noun.

Word	Noun	Adjective	Verb	Adverb
pay	Yes	No	Yes	No
prepay	No	No	Yes	No

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

pay (noun)	prepay (noun)
something that remunerates

pay (verb)	prepay (verb)
dedicate	pay for something before receiving it
bear (a cost or penalty), in recompense for some action
convey, as of a compliment, regards, attention, etc.; bestow
give money, usually in exchange for goods or services
bring in
do or give something to somebody in return
cancel or discharge a debt
make a compensation for
discharge or settle
render
be worth it