Language users use symbolic language expressions to communicate, and the meaning of sentences delivered is analyzed through correspondence with entities that exist in the real world. However, speakers do not always try to communicate based on the one world they belong to, and through a grammatical system called modality, they can communicate not only about the real world but also about the various possible worlds that exist. This means that statements about situations other than facts, i.e., hypothetical situations or states, can be expressed using modality, and the meaning of sentences can be analyzed through a concept of semantics as a possible world, and also through relevance theory in pragmatics. This study investigates the meaning of modal verbs through each of the two theories. First, the meaning of modal verbs is divided into necessity and possibility through existing research on modality. This analysis follows a definition of the core meaning of each modal verb through relevance theory, and evokes derivative meanings according to the context of occurrence. Possible world semantics, on the other hand, logically explains the various meanings of modal verbs by generating the real world and countless possible worlds through close connectivity using formal logical language of semantic representations from a polysemous perspective.