rate vs slowness

rate and slowness both are nouns.

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

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

rate (noun)	slowness (noun)
the relative speed of progress or change	a rate demonstrating an absence of haste or hurry
amount of a charge or payment relative to some basis	lack of normal development of intellectual capacities
a quantity or amount or measure considered as a proportion of another quantity or amount or measure	unskillfulness resulting from a lack of training
a magnitude or frequency relative to a time unit

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