rate vs interest rate

rate and interest rate both are nouns.

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

As nouns, interest rate is a hyponym of rate; that is, interest rate is a word with a more specific, narrower meaning than rate:

rate (noun)	interest rate (noun)
the relative speed of progress or change	the percentage of a sum of money charged for its use
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

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