mediator vs intermediary

mediator and intermediary both are nouns.

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

As nouns, mediator and intermediary are synonyms defined as:

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

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

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