piece rate vs pay

piece rate and pay both are nouns.

Word	Noun	Adjective	Verb	Adverb
piece rate	Yes	No	No	No
pay	Yes	No	Yes	No

As nouns, pay is a hypernym of piece rate; that is, pay is a word with a broader meaning than piece rate:

Other hypernyms of piece rate include earnings, remuneration, salary, wage.

piece rate (noun)	pay (noun)
a fixed rate paid according to the quantity produced.	something that remunerates

piece rate (verb)	pay (verb)
	dedicate
	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