independent agency vs authority

independent agency and authority both are nouns.

Word	Noun	Adjective	Verb	Adverb
independent agency	Yes	No	No	No
authority	Yes	No	No	No

As nouns, authority is a hypernym of independent agency; that is, authority is a word with a broader meaning than independent agency:

independent agency: an agency of the United States government that is created by an act of Congress and is independent of the executive departments
authority: an administrative unit of government

Other hypernyms of independent agency include agency, bureau, federal agency, government agency, office.

independent agency (noun)	authority (noun)
an agency of the United States government that is created by an act of Congress and is independent of the executive departments	the power or right to give orders or make decisions
	official permission or approval
	freedom from doubt; belief in yourself and your abilities
	an authoritative written work
	an administrative unit of government
	an expert whose views are taken as definitive
	(usually plural) persons who exercise (administrative) control over others