PHS vs government agency

PHS and government agency both are nouns.

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

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

PHS: an agency that serves as the office of Surgeon General; includes agencies whose mission is to improve the public health
government agency: an administrative unit of government

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

PHS (noun)	government agency (noun)
an agency that serves as the office of Surgeon General; includes agencies whose mission is to improve the public health	an administrative unit of government