unacknowledged vs secret

unacknowledged is not a noun while secret is a noun.

Word	Noun	Adjective	Verb	Adverb
unacknowledged	No	Yes	No	No
secret	Yes	Yes	No	No

unacknowledged (noun)	secret (noun)
	something that baffles understanding and cannot be explained
	something that should remain hidden from others (especially information that is not to be passed on)
	information known only to a special group

unacknowledged (adjective)	secret (adjective)
not recognized or admitted	the next to highest level of official classification for documents
not openly acknowledged	not open or public; kept private or not revealed
	having an import not apparent to the senses nor obvious to the intelligence; beyond ordinary understanding
	not expressed
	(of information) given in confidence or in secret
	not openly made known
	conducted with or marked by hidden aims or methods
	designed to elude detection
	indulging only covertly
	hidden from general view or use
	communicated covertly