sulkiness vs sullenness

sulkiness and sullenness both are nouns.

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

As nouns, sulkiness and sullenness are synonyms defined as:

Other synonyms of sulkiness include moroseness, sourness.

sulkiness (noun)	sullenness (noun)
a sullen moody resentful disposition	a sullen moody resentful disposition
a feeling of sulky resentment	a gloomy ill-tempered feeling
a mood or display of sullen aloofness or withdrawal