frightening vs fearful

frightening is a noun but fearful is not a noun.

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

As adjectives, frightening and fearful are synonyms defined as:

Other synonyms of frightening include awful, dire, direful, dread, dreaded, dreadful, fearsome, horrendous, horrific, terrible.

frightening (noun)	fearful (noun)
the act of inspiring with fear

frightening (adjective)	fearful (adjective)
causing fear or dread or terror	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