At the beginning of this book it was noted that it is possible to explore ideas about language change by looking at the internal history of a language and the external history of a language. Throughout this book so far the focus has been on the way external factors have influenced and are influencing language change. This final unit, however, will briefly summarise some of the more technical areas which have traditionally been at the heart of work on language change. In looking at such internal areas, though, it is important to stress again that language change always has a context and that language changes because of all the social, political and technological issues which affect the way language is used to communicate.