The module looks at the development of the English language, and examines its relationship with other, potentially rival, languages that have been spoken in the British Isles. It examines the effect of successive waves of conquest on the sociolinguistic situation which led to a situation of of diglossia or even triglossia, with English one of a number of varieties used in a set of socially determined domains. Using Haugen’s standardization model, we examine the factors which led first to selection and later acceptance of English as the dominant variety, and consider the associated linguistic processes of codification and elaboration of function. Working with short texts from different time periods, the module then introduces how and why grammatical changes occurred in Anglo-Saxon, Old and Middle English (e.g. loss of case marking, gender, weakening of the verbal paradigm) and their consequences for the modern language. We will also consider phonological changes (e.g. the Great English Vowel Shift) and their consequences for dialect differentiation. Throughout the module we make parallels with contemporary English by exploring ongoing change, including dialect loss and dialect levelling.