intermediary vs mediator

intermediary and mediator both are nouns.

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

As nouns, intermediary and mediator are synonyms defined as:

intermediary and mediator: a negotiator who acts as a link between parties

Other synonyms of intermediary include go-between, intercessor, intermediator.

intermediary (noun)	mediator (noun)
a negotiator who acts as a link between parties	a negotiator who acts as a link between parties