Editing Parameter (section)

==Logic==
In [[logic]], the parameters passed to (or operated on by) an ''open predicate'' are called ''parameters'' by some authors (e.g., [[Dag Prawitz|Prawitz]]'s ''Natural Deduction'';<ref>{{Prawitz Natural Deduction}}</ref> [[Lawrence Paulson|Paulson]]'s ''Designing a theorem prover''). Parameters locally defined within the predicate are called ''variables''. This extra distinction pays off when defining substitution (without this distinction special provision must be made to avoid variable capture). Others (maybe most) just call parameters passed to (or operated on by) an open predicate ''variables'', and when defining substitution have to distinguish between ''[[free variable]]s'' and ''[[bound variable]]s''.