flightiness vs irresponsibility

flightiness and irresponsibility both are nouns.

Word	Noun	Adjective	Verb	Adverb
flightiness	Yes	No	No	No
irresponsibility	Yes	No	No	No

As nouns, irresponsibility is a hypernym of flightiness; that is, irresponsibility is a word with a broader meaning than flightiness:

flightiness: the trait of acting unpredictably and more from whim or caprice than from reason or judgment
irresponsibility: a form of untrustworthiness; the trait of lacking a sense of responsibility and not feeling accountable for your actions

Other hypernyms of flightiness include irresponsibleness.

flightiness (noun)	irresponsibility (noun)
the trait of acting unpredictably and more from whim or caprice than from reason or judgment	a form of untrustworthiness; the trait of lacking a sense of responsibility and not feeling accountable for your actions