mediation vs dialogue

mediation and dialogue both are nouns.

Word	Noun	Adjective	Verb	Adverb
mediation	Yes	No	No	No
dialogue	Yes	No	No	No

As nouns, dialogue is a hypernym of mediation; that is, dialogue is a word with a broader meaning than mediation:

mediation: a negotiation to resolve differences that is conducted by some impartial party
dialogue: a discussion intended to produce an agreement

Other hypernyms of mediation include negotiation, talks.

mediation (noun)	dialogue (noun)
the act of intervening for the purpose of bringing about a settlement	the lines spoken by characters in drama or fiction
a negotiation to resolve differences that is conducted by some impartial party	a conversation between two persons
	a literary composition in the form of a conversation between two people
	a discussion intended to produce an agreement