Chapter 5 deals with the (posited) linguistic functions of abbreviation in the context of medieval manuscript textuality. It introduces the concept of communities of practice as framework for accounting for the socio-cultural context of abbreviating practices in England of the Middle Ages and outlines the tension between Latin and English as, respectively, the source and (creative) recipient of abbreviations. The chapter looks at linguistic contexts for abbreviation (that is, the morpho-lexical criteria informing the practice) and considers the visual diamorphy of abbreviations as elements belonging simultaneously to two linguistic codes. To address the Latin/ English interface in the interpretation of forms and functions of abbreviation symbols in Middle English manuscripts the chapter proposes the visual code-switching framework.