To exercise reason; to employ the mind in judging and inferring; to reason.
To engage in discussion or conversation; to converse.
To write or speak formally and at length.
Expression in words, either speech or writing.
A formal lengthy exposition of some subject, either spoken or written.
An institutionalized way of thinking, a social boundary defining what can be said about a specific topic (after Michel Foucault).
Any rational expression, reason.