This paper suggests that each modal verb has a single meaning. Proposing a monosemy view implies that modals have core meanings and a theory of pragmatics is required in order to give an explanation of how they get their different interpretations in the various contexts in which they occur. This paper adopts the relevance theory and explains which process causes a new relevant meaning from the core meaning. The two different views about the meaning of modal verbs are also examined: polysemy and Sweetser(1989)’s views. After introducing the basic claims and assumptions of these, this study suggests that they are not appropriate for modal verbs since they don’t present any solutions to some related problems. (Chungnam National University)