Formal work on axiomatic theories of truth has helped to shed some light on semantic theories of truth. For instance, it has yielded information on what is required of a metalanguage that is sufficient for defining a truth predicate. Semantic theories of truth, in turn, provide one with the theoretical tools needed for investigating models of axiomatic theories of truth and with motivations for certain axiomatic theories. Thus axiomatic and semantic approaches to truth are intertwined.