Editing Predicate variable (section)

{{Short description|Type of mathematical variable}}
In [[mathematical logic]], a '''predicate variable''' is a [[Predicate (mathematical logic)|predicate]] letter which functions as a "placeholder" for a [[Finitary relation|relation]] (between terms), but which has not been specifically assigned any particular relation (or meaning). Common symbols for denoting predicate variables include capital [[Latin script|roman letters]] such as <math>P</math>, <math>Q</math> and <math>R</math>, or lower case roman letters, e.g., <math>x</math>.<ref>{{Cite web|title=Predicate variable - Encyclopedia of Mathematics|url=https://encyclopediaofmath.org/wiki/Predicate_variable|access-date=2020-08-20|website=encyclopediaofmath.org}}</ref> In [[first-order logic]], they can be more properly called [[metalinguistic variable]]s. In [[higher-order logic]], predicate variables correspond to [[propositional variable]]s which can stand for [[well-formed formula]]s of the same logic, and such variables can be quantified by means of (at least) second-order [[Quantifier (logic)|quantifiers]].