sincerity vs serious-mindedness

sincerity and serious-mindedness both are nouns.

Word	Noun	Adjective	Verb	Adverb
sincerity	Yes	No	No	No
serious-mindedness	Yes	No	No	No

As nouns, sincerity and serious-mindedness are synonyms defined as:

Other synonyms of sincerity include earnestness, seriousness.

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