falling out vs separation

falling out and separation both are nouns.

Word	Noun	Adjective	Verb	Adverb
falling out	Yes	No	No	No
separation	Yes	No	No	No

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

Other hypernyms of falling out include breakup, detachment.

falling out (noun)	separation (noun)
a personal or social separation (as between opposing factions)	the social act of separating or parting company
	the act of dividing or disconnecting
	(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