separateness vs separation

separateness and separation both are nouns.

Word	Noun	Adjective	Verb	Adverb
separateness	Yes	No	No	No
separation	Yes	No	No	No

As nouns, separation is a hypernym of separateness; that is, separation is a word with a broader meaning than separateness:

separateness (noun)	separation (noun)
the quality of being not alike; being distinct or different from that otherwise experienced or known	the social act of separating or parting company
political independence	the act of dividing or disconnecting
the state of being several and distinct	(law) the cessation of cohabitation of man and wife (either by mutual agreement or under a court order)
	sorting one thing from others
	the distance between things
	coming apart
	the termination of employment (by resignation or dismissal)
	the space where a division or parting occurs
	the state of lacking unity