feed back vs feedback

feed back is not a noun while feedback is a noun.

Word	Noun	Adjective	Verb	Adverb
feed back	No	No	Yes	No
feedback	Yes	No	No	No

feed back (noun)	feedback (noun)
	response to an inquiry or experiment
	the process in which part of the output of a system is returned to its input in order to regulate its further output

feed back (verb)	feedback (verb)
respond to a query or outcome
submit (information) again to a program or automatic system