There is fairly general agreement that the modern reader's appreciation of Chaucer's writings can be enhanced by providing the reader with guides to `Chaucerian background' - literary, historical and cultural - and students of Chaucer are fortunate in having at their disposal a large number of books covering various aspects of Chaucerian background. One field which is less well covered is Chaucer's language: it is true that certain aspects of Chaucer's syntax and lexis have been dealt with in fairly recent years, but other subcategories of Chaucerian English, such as phonology and morphology, deserve more attention. The absence of readily available guides to these aspects of Chaucer's English has placed the linguistically-oriented student at a considerable disadvantage compared with his more literary-minded colleague, but the latter is also in need of a more detailed and reliable guide to Chaucerian English than the somewhat scant notes often included in editions of Chaucerian texts. The present book is intended to meet this need. It is largely limited to Chaucerian phonology and morphology, and assumes some familiarity with the rudiments of linguistics, but the technical terminology has been kept to a minimum.