dialogue vs diplomacy

dialogue and diplomacy both are nouns.

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

As nouns, diplomacy is a hyponym of dialogue; that is, diplomacy is a word with a more specific, narrower meaning than dialogue:

dialogue (noun)	diplomacy (noun)
the lines spoken by characters in drama or fiction	subtly skillful handling of a situation
a conversation between two persons	wisdom in the management of public affairs
a literary composition in the form of a conversation between two people	negotiation between nations
a discussion intended to produce an agreement