persona non grata vs diplomat

persona non grata and diplomat both are nouns.

Word	Noun	Adjective	Verb	Adverb
persona non grata	Yes	No	No	No
diplomat	Yes	No	No	No

As nouns, diplomat is a hypernym of persona non grata; that is, diplomat is a word with a broader meaning than persona non grata:

persona non grata: a diplomat who is unacceptable to the government to which he is sent
diplomat: an official engaged in international negotiations

Other hypernyms of persona non grata include diplomatist.

persona non grata (noun)	diplomat (noun)
a person who for some reason is not wanted or welcome	an official engaged in international negotiations
a diplomat who is unacceptable to the government to which he is sent	a person who deals tactfully with others