This book examines the concept of authentic English in today's world, where cultures are in constant interaction and the English language works as a binding agent for many cross-cultural exchanges. It offers a comprehensive review of decades of debate around authenticity in language teaching and learning and attempts to synthesise the complexities by presenting them as a continuum. This continuum builds on the work of eminent scholars and combines them within a flexible framework that celebrates the process of interaction whilst acknowledging the complexity and individual subjectivity of authenticity. Authenticity is approached as a complex dynamic construct that can only be understood by examining it from social, individual and contextual dimensions, in relation to actual people. Authenticity is a problem not just for language acquisition but one which affects us as individuals belonging to society.