What do you call the chair man in a debate?

There isn't a single, universally accepted term for the person who leads a debate. Here are some common options, depending on the context:

Formal:

* Moderator: This is the most common and neutral term, especially in formal debates.

* Chair: Similar to "moderator," this term is used in more formal settings.

* Presiding Officer: Used in very formal settings like parliamentary debates.

Informal:

* Facilitator: This term emphasizes the person's role in guiding the discussion.

* Host: This term is more common in informal debates, especially if the person also introduces the topic and participants.

* Judge: This term is used in competitive debates where someone evaluates the arguments presented.

Ultimately, the best term depends on the specific format of the debate and the person's role in it.