 Rigidity is generally discussed in the literature in connection with several theories about reference that were introduced or reintroduced or discussed feverishly about the time Kripke called attention to rigid designation. These theories address either the question of what it is that designating terms say or express or contribute to the content of propositions that they are used to articulate, or the question how it is that designating terms come to say or express or contribute the content they do. The relationship between rigidity and these other theories of reference, which is often blurred in the literature, can be brought into focus in a way that is fairly uncontroversial, in many instances.