A formula of the language of pure (or narrow) predicate calculus that is false in all models of this language. A formula is a contradiction if and only if is derivable in pure predicate calculus.
Contradiction (inconsistency). V.N. Grishin (originator), Encyclopedia of Mathematics. URL: http://www.encyclopediaofmath.org/index.php?title=Contradiction_(inconsistency)&oldid=13012