graveness vs somberness

graveness and somberness both are nouns.

Word	Noun	Adjective	Verb	Adverb
graveness	Yes	No	No	No
somberness	Yes	No	No	No

As nouns, graveness and somberness are synonyms defined as:

Other synonyms of graveness include gravity, soberness, sobriety, sombreness.

graveness (noun)	somberness (noun)
a manner that is serious and solemn	a manner that is serious and solemn
	a feeling of melancholy apprehension
	a state of partial or total darkness