fade out vs fadeout

fade out is not a noun while fadeout is a noun.

Word	Noun	Adjective	Verb	Adverb
fade out	No	No	Yes	No
fadeout	Yes	No	No	No

fade out (noun)	fadeout (noun)
	a slow or gradual disappearance
	a gradual temporary loss of a transmitted signal due to electrical disturbances

fade out (verb)	fadeout (verb)
grow less and less substantial until it disappears