seriousness vs serious-mindedness

seriousness and serious-mindedness both are nouns.

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

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

Other synonyms of seriousness include earnestness, sincerity.

seriousness (noun)	serious-mindedness (noun)
the trait of being serious	the trait of being serious
the quality of arousing fear or distress
an earnest and sincere feeling