This comprehensive, up-to-date, and accessible text on idiom use, learning, and teaching approaches the topic with a balance of sound theory and extensive research in cognitive linguistics, psycholinguistics, corpus linguistics, and sociolinguistics combined with informed teaching practices. Idioms is organized into three parts: Part I includes discussion of idiom definition, classification, usage patterns, and functions. Part II investigates the process involved in the comprehension of idioms and the factors that influence individuals’ understanding and use of idioms in both L1 and L2. Part III explores idiom acquisition and the teaching and learning of idioms, focusing especially on the strategies and techniques used to help students learn idioms. To assist the reader in grasping the key issues, study questions are provided at the end of each chapter. The text also includes a glossary of special terms and an annotated list of selective idiom reference books and student textbooks. Idioms is designed to serve either as a textbook for ESL/applied linguistics teacher education courses or as a reference book. No matter how the book is used, it will equip ESL/applied linguistics students and professionals with a solid understanding of various issues related to idioms and the learning of them.