Definition:Variable/Predicate Logic

Definition
In the context of predicate logic, a variable is often called an object variable or arbitrary name.

As such, it is a symbol which is assigned to an arbitrarily selected object from a given universe of discourse.

The understanding is that (during the scope of the argument to which it is relevant) the arbitrary name could apply equally well to any of the objects in that universe.

Also see

 * Propositional function