The number of English speakers in the world continues to grow, but the vast majority are non-native speakers using English to communicate with each other, rather than with native speakers. This book examines the use of English as a Lingua Franca (ELF) from various perspectives. It explores the various ways in which ELF represents a challenge to the predominance of the native-speaker model, as well as its implications for other fields of linguistic research and for English language teaching.