How and why do languages change? This new introduction offers a guide to the types of change at all levels of linguistic structure, as well as the mechanisms behind each type. Based on data from a variety of methods and a huge array of language families, it examines general patterns of change, bringing together recent findings on sound change, analogical change, grammaticalization, the creation and change of constructions, as well as lexical change. Emphasizing crosslinguistic patterns and going well beyond traditional methods in historical linguistics, this book sees change as grounded in cognitive processes and usage factors that are rarely mentioned in other textbooks. Complete with questions for discussion, suggested readings and a useful glossary of terms, this book helps students to gain a general understanding of language as an ever-changing system.