USAF vs bureau

USAF and bureau both are nouns.

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

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

USAF: the airforce of the United States of America; the agency that defends the United States through control and exploitation of air and space
bureau: an administrative unit of government

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

USAF (noun)	bureau (noun)
the airforce of the United States of America; the agency that defends the United States through control and exploitation of air and space	furniture with drawers for keeping clothes
	an administrative unit of government