seriousness vs sincerity

seriousness and sincerity both are nouns.

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

As nouns, seriousness and sincerity are synonyms defined as:

Other synonyms of seriousness include earnestness, serious-mindedness.

As nouns, seriousness and sincerity are synonyms defined as:

Other synonyms of seriousness include earnestness.

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