indefinability vs inability

indefinability and inability both are nouns.

Word	Noun	Adjective	Verb	Adverb
indefinability	Yes	No	No	No
inability	Yes	No	No	No

As nouns, inability is a hypernym of indefinability; that is, inability is a word with a broader meaning than indefinability:

indefinability: The quality of not being able to be precisely defined or put into words.
inability: lacking the power to perform

Other hypernyms of indefinability include indefiniteness, indefinity, indeterminacy, indeterminateness, indetermination, unfitness.

indefinability (noun)	inability (noun)
The quality of not being able to be precisely defined or put into words.	lacking the power to perform
	lack of ability (especially mental ability) to do something