graveness vs sombreness

graveness and sombreness both are nouns.

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

As nouns, graveness and sombreness are synonyms defined as:

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

graveness (noun)	sombreness (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