fearful vs fearfulness

fearful is not a noun while fearfulness is a noun.

Word	Noun	Adjective	Verb	Adverb
fearful	No	Yes	No	No
fearfulness	Yes	No	No	No

fearful (noun)	fearfulness (noun)
	the trait of being afraid
	an emotion experienced in anticipation of some specific pain or danger (usually accompanied by a desire to flee or fight)

fearful (adjective)	fearfulness (adjective)
lacking courage; ignobly timid and faint-hearted
experiencing or showing fear
causing fear or dread or terror
extremely distressing
timid by nature or revealing timidity