FAA vs bureau

FAA and bureau both are nouns.

Word	Noun	Adjective	Verb	Adverb
FAA	Yes	No	No	No
bureau	Yes	No	No	No

As nouns, bureau is a hypernym of FAA; that is, bureau is a word with a broader meaning than FAA:

FAA: an agency in the Department of Transportation that is responsible for the safety of civilian aviation
bureau: an administrative unit of government

Other hypernyms of FAA include agency, authority, federal agency, government agency, office.

FAA (noun)	bureau (noun)
an agency in the Department of Transportation that is responsible for the safety of civilian aviation	furniture with drawers for keeping clothes
	an administrative unit of government