This text offers a comprehensive introduction to vocabulary for language teachers who would like to know more about the way vocabulary works. It provides the background knowledge necessary for practitioners to make informed choices about vocabulary teaching and testing. The overall theme is making research and theory accessible, and then drawing on it to suggest effective classroom applications. Chapters 1 and 2 provide linguistic and historical background. Chapters 3-7 describe the various kinds of knowledge a person can have about a word, how vocabulary behaves in context, and how it is acquired. Chapters 8 and 9 focus on issues in teaching and testing vocabulary. The chapters include teaching applications, exercises, and suggestions for further reading. The appendices include a word list of academic vocabulary and a vocabulary test.