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In mathematical logic, a propositional variable (also called a sentential variable or sentential letter) is a variable which can either be true or false. Propositional variables are the basic building-blocks of propositional formulas, used in propositional logic and higher logics. ==Uses== Formulas in logic are typically built up recursively from some propositional variables, some number of logical connectives, and some logical quantifiers. Propositional variables are the atomic formulas of propositional logic. ;Example In a given propositional logic, we might define a formula as follows: *Every propositional variable is a formula. *Given a formula ''X'' the negation ''¬X'' is a formula. *Given two formulas ''X'' and ''Y'', and a binary connective ''b'' (such as the logical conjunction ∧), then ''(X b Y)'' is a formula. (Note the parentheses.) In this way, all of the formulas of propositional logic are built up from propositional variables as a basic unit. Propositional variables should not be confused with the metavariables which appear in the typical axioms of propositional calculus; the latter effectively range over well-formed formulae. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Propositional variable」の詳細全文を読む スポンサード リンク
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