earnestness vs serious-mindedness

earnestness and serious-mindedness both are nouns.

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

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

Other synonyms of earnestness include seriousness, sincerity.

earnestness (noun)	serious-mindedness (noun)
the trait of being serious	the trait of being serious
an earnest and sincere feeling