fadeout vs fade out

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

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

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

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