Dialogue, n.
Etymology: [OE. dialogue, L. dialogus, fr. Gr. dialogue. See Legend.]
1. A conversation between two or more persons; particularly, a formal conservation in theatrical performances or in scholastic exercises.
2. A written composition in which two or more persons are represented as conversing or reasoning on some topic; as, the Dialogues of Plato.
2 other Webster entries under this spelling
Dialogue, v. i.
To take part in a dialogue; to dialogize. [R.] Shak.
Dialogue, v. t.
To express as in dialogue. [R.] And dialogued for him what he would say. Shak.
Shades of meaning
Fernald has no entry of its own for dialogue; he lists it under conversation.
He lists it without comment; the entries above explain its neighbors.