falling out vs severance

falling out and severance both are nouns.

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

As nouns, falling out and severance are synonyms defined as:

falling out and severance: a personal or social separation (as between opposing factions)

Other synonyms of falling out include breach, break, rift, rupture.

falling out (noun)	severance (noun)
a personal or social separation (as between opposing factions)	the act of severing
	a personal or social separation (as between opposing factions)