This chapter discusses the ongoing enterprise of developing typologies of writing systems, which strives to propose a coherent framework for classifying the world’s diverse writing systems. Because different theoretical assumptions about the core entities under analysis can yield divergent proposals, it is valuable to continually assess the conceptual and terminology contrasts that both shape and communicate typology proposals. Therefore, this chapter examines the underlying conceptualizations, the diverse, and often inconsistent, terminology, and the main limitations of existing typologies of writing systems, to further elucidate the materialization of written language both diachronically and synchronically. The substantial third section illustrates how the majority of typology proposals classify writing systems primarily in terms of a core set of representational principles, or mapping relationships, assumed to exist between the linguistic units and graphemes of a language. After commenting on the elusive trinity of key terms (writing system, script and orthography), this section outlines some of the most influential, controversial and promising typology proposals and reflects on the various conceptual and terminological distinctions propounded to capture the principles of representational mapping. The last section of the chapter briefly considers the merits of exploring complementary or alternative approaches to writing system typologies.