Predicate constant is a basic expression in predicate logic denoting properties of or relations between individuals. One-place predicate constants combine with one individual term: P(a), two-place predicates with two individual terms: R(b,c), etcetera. One-place predicates are interpreted as sets, n-place predicates with n > 1 as sets of ordered pairs. In 'higher-order' predicate logic and in type logic, it is also possible for a predicate to take another predicate as an argument. Predicates which take other predicates as their argument are called second-order predicates.
- Gamut, L.T.F. 1991. Logic, language, and meaning, Univ. of Chicago Press, Chicago.