Propositional form

A linguistic expression containing variables, in place of which one may substitute propositions, thereby obtaining new propositions. In formalized languages a propositional form is a formula containing free occurrences of propositional variables taking values in the set of truth values (cf. Truth value).

Sometimes a propositional form is an expression, constructed in analogy with a propositional formula, in which symbols of a meta-language are used instead of propositional variables, and denoting arbitrary formulas of the propositional calculus.

References

[1]	E. Mendelson, "Introduction to mathematical logic" , v. Nostrand (1964)