sulkiness vs bitterness

sulkiness and bitterness both are nouns.

Word	Noun	Adjective	Verb	Adverb
sulkiness	Yes	No	No	No
bitterness	Yes	No	No	No

As nouns, bitterness is a hypernym of sulkiness; that is, bitterness is a word with a broader meaning than sulkiness:

Other hypernyms of sulkiness include gall, rancor, rancour, resentment.

sulkiness (noun)	bitterness (noun)
a sullen moody resentful disposition	the property of having a harsh unpleasant taste
a feeling of sulky resentment	a rough and bitter manner
a mood or display of sullen aloofness or withdrawal	the taste experience when quinine or coffee is taken into the mouth
	a feeling of deep and bitter anger and ill-will