This book was written for university students of English/English Linguistics/English Philology. The first part of the book contains three sections. The first of them introduces several methods which are applied in diachronic linguistics, the second deals with the kind of data which lend themselves as starting-points for hypotheses about linguistic changes, and the third presents constellations which are prone to trigger such changes. The second part describes the most important developments of the English Language on the structural levels of phonology, grammar, word-formation and lexicology. On the one hand, these developments are illustrated with new material, on the other, with examples the reader is already familiar with from part one. The book is suitable as a text-book for introductory courses to diachronic English linguistics, but it can also be profitably read on its own as well as serve recap purposes.