lightheadedness vs heedlessness

lightheadedness and heedlessness both are nouns.

Word	Noun	Adjective	Verb	Adverb
lightheadedness	Yes	No	No	No
heedlessness	Yes	No	No	No

As nouns, heedlessness is a hypernym of lightheadedness; that is, heedlessness is a word with a broader meaning than lightheadedness:

Other hypernyms of lightheadedness include mindlessness, rashness.

lightheadedness (noun)	heedlessness (noun)
a frivolous lack of prudence	the trait of forgetting or ignoring your responsibilities
a reeling sensation; a feeling that you are about to fall	the trait of acting rashly and without prudence
	a lack of attentiveness (as to children or helpless people)