ONI vs government agency

ONI and government agency both are nouns.

Word	Noun	Adjective	Verb	Adverb
ONI	Yes	No	No	No
government agency	Yes	No	No	No

As nouns, government agency is a hypernym of ONI; that is, government agency is a word with a broader meaning than ONI:

ONI: the military intelligence agency that provides for the intelligence and counterintelligence and investigative and security requirements of the United States Navy
government agency: an administrative unit of government

Other hypernyms of ONI include agency, authority, bureau, federal agency, office.

ONI (noun)	government agency (noun)
the military intelligence agency that provides for the intelligence and counterintelligence and investigative and security requirements of the United States Navy	an administrative unit of government