This textbook approaches the history of English from a theoretical perspective. The book provides a brief chronological overview describing the way in which the English language has changed over time from Old English to Modern English, while subsequent parts adopt a theoretical focus that is thematically organised to deal with the question of how and why English changed in the way it did, including a part addressing some specific contact-induced changes and key topics such as English as a Lingua Franca. Supported throughout with information boxes with empirical studies, the examples given are all drawn from English, but boxes with examples from other languages tie the development of the English language into changes in other contexts and settings. This book is an ideal resource for undergraduate students of the English Language and historical linguistics.