bitterness vs thorniness

bitterness and thorniness both are nouns.

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

As nouns, bitterness and thorniness are synonyms defined as:

Other synonyms of bitterness include acerbity, acrimony, jaundice, tartness.

bitterness (noun)	thorniness (noun)
the property of having a harsh unpleasant taste	the quality of being covered with prickly thorns or spines
a rough and bitter manner	a rough and bitter manner
the taste experience when quinine or coffee is taken into the mouth	The property of being full of difficulties, complexities, or controversial points.
a feeling of deep and bitter anger and ill-will