In modern society, the question of what a particular verbal or nonverbal sign represents is an important issue. One may assume that a certain sign has a definite set of static meanings; however, close examination reveals that, in theory, it has an indefinite number of meanings in real communication. A meaning of a sign is a dynamic entity to be produced in the process of its interaction with surrounding situations. Since such situations are indefinite in number, what a sign may mean could be indefinitely extended. This course investigates how a meaning could be produced in situations. We will focus on modal verbs, since they are linguistic signs that literally incorporate non-linguistic situations. Students interested in pursuing this course should have taken a course in language and communication.