somberness vs sincerity

somberness and sincerity both are nouns.

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

As nouns, sincerity is a hypernym of somberness; that is, sincerity is a word with a broader meaning than somberness:

Other hypernyms of somberness include earnestness, serious-mindedness, seriousness.

somberness (noun)	sincerity (noun)
a manner that is serious and solemn	the quality of being open and truthful; not deceitful or hypocritical
a feeling of melancholy apprehension	the trait of being serious
a state of partial or total darkness	a quality of naturalness and simplicity
	an earnest and sincere feeling