imperfectness vs fault

imperfectness and fault both are nouns.

Word	Noun	Adjective	Verb	Adverb
imperfectness	Yes	No	No	No
fault	Yes	No	Yes	No

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

Other hyponyms of imperfectness include failing, weakness, flaw, defect, defect, flaw, wart, defectiveness, faultiness, nonoptimality.

imperfectness (noun)	fault (noun)
the state or an instance of being imperfect	a wrong action attributable to bad judgment or ignorance or inattention
	(sports) a serve that is illegal (e.g., that lands outside the prescribed area)
	the quality of being inadequate or falling short of perfection
	responsibility for a bad situation or event
	(electronics) equipment failure attributable to some defect in a circuit (loose connection or insulation failure or short circuit etc.)
	(geology) a crack in the earth's crust resulting from the displacement of one side with respect to the other
	an imperfection in an object or machine

imperfectness (verb)	fault (verb)
	put or pin the blame on