 Properties are expressed, as meanings, by predicates. In the past “predicate” was often used as synonym of “property”, but nowadays predicates are linguistic entities, typically contrasted with singular terms, i.e., simple or complex noun phrases such as “Daniel”, “this horse” or “the President of France”, which can occupy subject positions in sentences and purport to denote, or refer to, a single thing. Following Frege, predicates are verbal phrases such as “is French” or “drinks”. Alternatively, predicates are general terms such as “French”, with the copula “is” (or verbal inflection) taken to convey an exemplification link (P. Strawson 1959; Bergmann 1960). We shall conveniently use “predicate” in both ways. Predicates are predicated of singular terms, thereby generating sentences such as “Daniel is French”. In the familiar formal language of first-order logic, this would be rendered, say, as “\(F(d)\)”, thus representing the predicate with a capital letter. The set or class of objects to which a predicate veridically applies is often called the extension of the predicate, or of the corresponding property. This property, in contrast, is called the intension of the predicate, i.e., its meaning. This terminology traces back to the Middle Age and in the last century has led to the habit of calling sets and properties extensional and intensional entities, respectively. Extensions and intensions can hardly be identified; this is immediately suggested by paradigmatic examples of co-extensional predicates that appear to differ in meaning, such as “has a heart”, and “has kidneys” (see  §3.1).