resentment vs bitterness

resentment and bitterness both are nouns.

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

As nouns, resentment and bitterness are synonyms defined as:

resentment and bitterness: a feeling of deep and bitter anger and ill-will

Other synonyms of resentment include gall, rancor, rancour.

resentment (noun)	bitterness (noun)
a feeling of deep and bitter anger and ill-will	the property of having a harsh unpleasant taste
	a rough and bitter manner
	the taste experience when quinine or coffee is taken into the mouth
	a feeling of deep and bitter anger and ill-will