United States Navy vs bureau

United States Navy and bureau both are nouns.

Word	Noun	Adjective	Verb	Adverb
United States Navy	Yes	No	No	No
bureau	Yes	No	No	No

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

United States Navy: the navy of the United States of America; the agency that maintains and trains and equips combat-ready naval forces
bureau: an administrative unit of government

Other hypernyms of United States Navy include agency, authority, federal agency, government agency, office.

United States Navy (noun)	bureau (noun)
the navy of the United States of America; the agency that maintains and trains and equips combat-ready naval forces	furniture with drawers for keeping clothes
	an administrative unit of government