A symbol is something which is determined by something else for someone. For example, the sound /crow/ evokes the image of a crow, a large, black bird. Words are typical examples of symbols, but symbols are not limited to words. For example, the cawing of a crow signifies the approach of evening, and scattered garbage at a dump suggest that crows have scavenged there. These are all examples of symbols. The nature of symbols has long attracted the interest of psychologists, linguists, and philosophers because it explains the process of generating meanings. The study of symbols has traditionally been developed through two theoretical frameworks: semiotics, grounded in the work of Charles Sanders Peirce, and semiology, developed by Ferdinand de Saussure. This chapter provides an overview of these two approaches to symbols and discusses their relevance to symbol emergence systems theory.