solemness vs sincerity

solemness and sincerity both are nouns.

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

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

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

solemness (noun)	sincerity (noun)
a trait of dignified seriousness	the quality of being open and truthful; not deceitful or hypocritical
	the trait of being serious
	a quality of naturalness and simplicity
	an earnest and sincere feeling