The historical development of a language is often thought of in terms of the history of the structural linguistic material of a language, i.e. its lexis, its phonology, its syntax and morphology. Specifically with respect to English there in quite a number of aspects of its development over a thousand years a debate about the relative share of internal, structural factors and language-external factors, such as the effect of language contact on the structural history of English. This class emphasizes the ”external” aspects of the history of English, i.e. the contribution of historical, social and sociological developments in which the structural and varietal history is embedded and which are hypothesized to account for aspects of its history. ”Historical” in this case implies not only closed developments, but includes ongoing varietal developments into present-day English.