serious vs serious-mindedness

serious is not a noun while serious-mindedness is a noun.

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

serious (noun)	serious-mindedness (noun)
	the trait of being serious

serious (adjective)	serious-mindedness (adjective)
concerned with work or important matters rather than play or trivialities
completely lacking in playfulness
causing fear or anxiety by threatening great harm
requiring effort or concentration; complex and not easy to answer or solve
of great consequence
appealing to the mind