clumsiness vs slowness

clumsiness and slowness both are nouns.

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

As nouns, clumsiness and slowness are synonyms defined as:

clumsiness and slowness: unskillfulness resulting from a lack of training

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

clumsiness (noun)	slowness (noun)
the carriage of someone whose movements and posture are ungainly or inelegant	a rate demonstrating an absence of haste or hurry
the inelegance of someone stiff and unrelaxed (as by embarrassment)	lack of normal development of intellectual capacities
unskillfulness resulting from a lack of training	unskillfulness resulting from a lack of training