sincerity vs seriousness

sincerity and seriousness both are nouns.

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

As nouns, sincerity and seriousness are synonyms defined as:

Other synonyms of sincerity include earnestness, serious-mindedness.

As nouns, sincerity and seriousness are synonyms defined as:

Other synonyms of sincerity include earnestness.

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