OSHA vs bureau

OSHA and bureau both are nouns.

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

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

OSHA: a government agency in the Department of Labor to maintain a safe and healthy work environment
bureau: an administrative unit of government

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

OSHA (noun)	bureau (noun)
a government agency in the Department of Labor to maintain a safe and healthy work environment	furniture with drawers for keeping clothes
	an administrative unit of government