in mathematical logic
A logical formula that becomes a true proposition under any interpretation of the variables for propositions and predicates that occur in it. Such formulas are called generally valid, universally valid or tautologies. For example, the tautology $A\lor\neg A$ expresses the law of the excluded middle.
|[a1]||A. Grzegorczyk, "An outline of mathematical logic" , Reidel (1974)|
Logical law. Encyclopedia of Mathematics. URL: http://encyclopediaofmath.org/index.php?title=Logical_law&oldid=31440