imperfectness vs flaw

imperfectness and flaw both are nouns.

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

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

imperfectness: the state or an instance of being imperfect
flaw: an imperfection in a plan or theory or legal document that causes it to fail or that reduces its effectiveness

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

imperfectness (noun)	flaw (noun)
the state or an instance of being imperfect	an imperfection in an object or machine
	defect or weakness in a person's character
	an imperfection in a plan or theory or legal document that causes it to fail or that reduces its effectiveness

imperfectness (verb)	flaw (verb)
	add a flaw or blemish to; make imperfect or defective