Customs Bureau vs bureau

Customs Bureau and bureau both are nouns.

Word	Noun	Adjective	Verb	Adverb
Customs Bureau	Yes	No	No	No
bureau	Yes	No	No	No

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

Customs Bureau: the agency of the Treasury Department that enforces import tariffs
bureau: an administrative unit of government

Other hypernyms of Customs Bureau include agency, authority, federal agency, government agency, office.

Customs Bureau (noun)	bureau (noun)
the agency of the Treasury Department that enforces import tariffs	furniture with drawers for keeping clothes
	an administrative unit of government