pay rate vs rate

pay rate and rate both are nouns.

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

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

Other hypernyms of pay rate include charge per unit.

pay rate (noun)	rate (noun)
amount of money received per unit time	the relative speed of progress or change
	amount of a charge or payment relative to some basis
	a quantity or amount or measure considered as a proportion of another quantity or amount or measure
	a magnitude or frequency relative to a time unit

pay rate (verb)	rate (verb)
	assign a rank or rating to
	estimate the value of
	be worthy of or have a certain rating