English seems both prolific and eclectic in its borrowing practices. While certain languages, such as French, predominate as sources for borrowings into English, there are very few languages with a large number of speakers which have not provided words and phrases to the language. This chapter discusses different types of lexical borrowing while providing a deeper analysis of a set of morphosyntactic changes through which English passed in the period from around 800 to 1100 CE, suggesting a contact-derived catalyst underlying them. The English language has been affected considerably by the languages of immigrants. Some of these have proved of great consequence in relation to its later development. Cultural prestige has also encouraged borrowing and other phenomena into English. Typologically, English experienced a striking change in direction from a rather synthetic morphosyntactic nature to one which exhibited strong analytic tendencies. Three major external influences affected the English language: Celtic, Norse, and French.