sombreness vs gravity

sombreness and gravity both are nouns.

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

As nouns, sombreness and gravity are synonyms defined as:

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

sombreness (noun)	gravity (noun)
a manner that is serious and solemn	a manner that is serious and solemn
a feeling of melancholy apprehension	a solemn and dignified feeling
a state of partial or total darkness	(physics) the force of attraction between all masses in the universe; especially the attraction of the earth's mass for bodies near its surface