<logic> In predicate logic, a function from individuals to truth-values. A wff of predicate logic with at least one free variable. An open wff. A propositional function becomes a proposition when it is closed (see closure of a wff); it is closed either by generalization or instantiation, that is, either by binding free variables or replacing them with constants.
See generalization, instantiation, wff, open
[Glossary of First-Order Logic]
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