 The features of modal logic most relevant to this entry on many-sorted logic are that truth can be qualified (or relativized) and that modal models include a universe of what are called “possible worlds”. The classical semantical concept of truth in a model, written as \(\mathcal{A}\models \varphi\) is now replaced by truth at a world \(w\) in a model \(\mathcal{A}\), written as \(\mathcal{A},w\models \varphi\).