pace vs slowness

pace and slowness both are nouns.

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

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

pace (noun)	slowness (noun)
a step in walking or running	a rate demonstrating an absence of haste or hurry
the relative speed of progress or change	lack of normal development of intellectual capacities
a unit of length equal to 3 feet; defined as 91.44 centimeters; originally taken to be the average length of a stride	unskillfulness resulting from a lack of training
the distance covered by a step
the rate of moving (especially walking or running)
the rate of some repeating event