diplomat vs intermediary

diplomat and intermediary both are nouns.

Word	Noun	Adjective	Verb	Adverb
diplomat	Yes	No	No	No
intermediary	Yes	No	No	No

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

Other hypernyms of diplomat include go-between, intercessor, intermediator, mediator.

diplomat (noun)	intermediary (noun)
an official engaged in international negotiations	a negotiator who acts as a link between parties
a person who deals tactfully with others