slowness vs ineptitude

slowness and ineptitude both are nouns.

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

As nouns, slowness and ineptitude are synonyms defined as:

slowness and ineptitude: unskillfulness resulting from a lack of training

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

slowness (noun)	ineptitude (noun)
a rate demonstrating an absence of haste or hurry	having no qualities that would render it valuable or useful
lack of normal development of intellectual capacities	unskillfulness resulting from a lack of training
unskillfulness resulting from a lack of training