dumbness vs slow-wittedness

dumbness and slow-wittedness both are nouns.

Word	Noun	Adjective	Verb	Adverb
dumbness	Yes	No	No	No
slow-wittedness	Yes	No	No	No

As nouns, dumbness and slow-wittedness are synonyms defined as:

dumbness and slow-wittedness: the quality of being mentally slow and limited

Other synonyms of dumbness include denseness.

dumbness (noun)	slow-wittedness (noun)
the quality of being mentally slow and limited	the quality of being mentally slow and limited