Formal:
* Dialogue: A formal discussion between two or more people.
* Discourse: A serious and extended discussion or debate.
* Parley: A discussion, especially one between enemies.
* Communiqué: An official announcement or statement.
Informal:
* Chat: A casual and friendly conversation.
* Talk: A general term for spoken communication.
* Discussion: A conversation where different points of view are exchanged.
* Debate: A formal argument about a specific topic.
* Dialogue: Used more broadly than in formal contexts.
Other:
* Exchange: A back-and-forth interaction between two or more people.
* Interchange: A two-way flow of information or ideas.
* Rapport: A harmonious relationship or understanding.
* Banter: Light-hearted and playful conversation.
The best word to use depends on the specific situation and the tone you want to convey.