bitterness vs grievance

bitterness and grievance both are nouns.

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

As nouns, grievance is a hyponym of bitterness; that is, grievance is a word with a more specific, narrower meaning than bitterness:

Other hyponyms of bitterness include heartburning, huffishness, sulkiness, grudge, score, enviousness, envy.

bitterness (noun)	grievance (noun)
the property of having a harsh unpleasant taste	a complaint about a (real or imaginary) wrong that causes resentment and is grounds for action
a rough and bitter manner	an allegation that something imposes an illegal obligation or denies some legal right or causes injustice
the taste experience when quinine or coffee is taken into the mouth	a resentment strong enough to justify retaliation
a feeling of deep and bitter anger and ill-will