dialog vs duologue

dialog and duologue both are nouns.

Word	Noun	Adjective	Verb	Adverb
dialog	Yes	No	No	No
duologue	Yes	No	No	No

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

dialog: the lines spoken by characters in drama or fiction
duologue: a part of the script in which the speaking roles are limited to two actors

As nouns, dialog and duologue are synonyms defined as:

Other synonyms of dialog include dialogue.

dialog (noun)	duologue (noun)
the lines spoken by characters in drama or fiction	a part of the script in which the speaking roles are limited to two actors
a conversation between two persons	a conversation between two persons
a literary composition in the form of a conversation between two people