spend vs pay

spend is not a noun while pay is a noun.

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

As verbs, pay is a hypernym of spend; that is, pay is a word with a broader meaning than spend:

Other hypernyms of spend include consume, deplete, eat, eat up, exhaust, expend, run through, use, use up, wipe out.

spend (noun)	pay (noun)
	something that remunerates

spend (verb)	pay (verb)
pay out	dedicate
spend completely	bear (a cost or penalty), in recompense for some action
use up a period of time in a specific way	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