aptitude vs capableness

aptitude and capableness both are nouns.

Word	Noun	Adjective	Verb	Adverb
aptitude	Yes	No	No	No
capableness	Yes	No	No	No

As nouns, capableness is a hyponym of aptitude; that is, capableness is a word with a more specific, narrower meaning than aptitude:

Other hyponyms of aptitude include inherent aptitude, instinct, capability, potentiality, natural ability.

aptitude (noun)	capableness (noun)
inherent ability	the quality of being capable -- physically or intellectually or legally
	an aptitude that may be developed