incapacity vs incapableness

incapacity and incapableness both are nouns.

Word	Noun	Adjective	Verb	Adverb
incapacity	Yes	No	No	No
incapableness	Yes	No	No	No

As nouns, incapableness is a hypernym of incapacity; that is, incapableness is a word with a broader meaning than incapacity:

incapacity: lack of physical or natural qualifications
incapableness: the quality of not being capable -- physically or intellectually or legally

Other hypernyms of incapacity include incapability.

incapacity (noun)	incapableness (noun)
lack of physical or natural qualifications	the quality of not being capable -- physically or intellectually or legally
lack of intellectual power	lack of potential for development