rate vs tax rate

rate and tax rate both are nouns.

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

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

rate (noun)	tax rate (noun)
the relative speed of progress or change	rate used to calculate tax liability
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)	tax rate (verb)
assign a rank or rating to
estimate the value of
be worthy of or have a certain rating