A notion introduced by Florentin Smarandache: An element x(T, I, F) belongs more than sure to the set M; here T, I, F are real subsets representing the truth, indeterminacy, and falsity percentages respectively, and sup(T)>100.

tautological set are used for universally true propositions where no parameter such as time, space, or subjectivity influences the truth value.

[Florentin Smarandache, "A Unifying Field in Logics. / Neutrosophy: Neutrosophic Probability, Set, and Logic", American Research Press, Rehoboth, 1999]