Languages undergo continual change, but not at constant speed. External and internal dynamics affect the speed as well as the different scales at which change occurs. Among important external factors, societal change, mobility and the ensuing language contact create conditions of stability or instability and upheaval. Language-internal changes may be triggered off by external changes, for instance when these lead to lively contact between languages or varieties, but internal changes may also begin seemingly autonomously, and may affect different subsystems, or one or more subsystems at different stages. In this volume both internal and external processes of language change are addressed, with a focus on contemporary processes and on English, although not exclusively, so that historical lines of development are included, as are other languages. Throughout the volume, the contributions highlight social contexts of various sizes and kinds, and social processes interacting with linguistic ones. A few chapters also delve into cognitive processes and individual users, thus ensuring that a range of scales is covered in addressing the issues of change and the specific phenomenon of English as a global lingua franca.

This chapter covers factors that affect variation in phonological or prosodic form synchronically and diachronically. Such factors can include grammatical context, phonetic factors such as ease of articulation and perception, as well as a range of sociolinguistic factors, such as age, gender, region, and ethnicity.