falling out vs breach

falling out and breach both are nouns.

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

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

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

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

falling out (noun)	breach (noun)
a personal or social separation (as between opposing factions)	a failure to perform some promised act or obligation
	a personal or social separation (as between opposing factions)
	an opening (especially a gap in a dike or fortification)

falling out (verb)	breach (verb)
	make an opening or gap in
	act in disregard of laws, rules, contracts, or promises