authorities vs regime

authorities and regime both are nouns.

Word	Noun	Adjective	Verb	Adverb
authorities	Yes	No	No	No
regime	Yes	No	No	No

As nouns, authorities and regime are synonyms defined as:

authorities and regime: the organization that is the governing authority of a political unit

Other synonyms of authorities include government.

authorities (noun)	regime (noun)
the organization that is the governing authority of a political unit	(medicine) a systematic plan for therapy (often including diet)
	the organization that is the governing authority of a political unit