Customs Service vs bureau

Customs Service and bureau both are nouns.

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

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

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

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

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