 Montague semantics is not interested in a particular situation (e.g. the real world) but in semantical properties of language. When formalizing such properties, reference to a class of models has to be made, and therefore the interpretation of a language will be defined with respect to a set of (suitable) models. For example, in the introduction we mentioned that the characterization of entailment was a basic goal of semantics. That notion is defined as follows. Sentence \(A\) entails sentence \(B\) if in all models in which the interpretation of \(A\) is true, also the interpretation of \(B\) is true. Likewise, a tautology is true in all models, and a contradiction is true in no model.