slowness vs ineptness

slowness and ineptness both are nouns.

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

As nouns, slowness and ineptness are synonyms defined as:

slowness and ineptness: unskillfulness resulting from a lack of training

Other synonyms of slowness include awkwardness, clumsiness, ineptitude, maladroitness.

slowness (noun)	ineptness (noun)
a rate demonstrating an absence of haste or hurry	the quality of having the wrong properties for a specific purpose
lack of normal development of intellectual capacities	unskillfulness resulting from a lack of training
unskillfulness resulting from a lack of training