awful vs frightening

awful is not a noun while frightening is a noun.

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

As adjectives, awful and frightening are synonyms defined as:

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

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

awful (adjective)	frightening (adjective)
offensive or even (of persons) malicious	causing fear or dread or terror
causing fear or dread or terror
exceptionally bad or displeasing
extreme in degree or extent or amount or impact
inspiring awe or admiration or wonder
inspired by a feeling of fearful wonderment or reverence

awful (adverb)	frightening (adverb)
used as intensifiers