This wide-ranging book, focused on the use of English as a lingua franca in intranational and international contexts, explores the ecologies in which interactions in English occur and the phonological, grammatical, lexical and pragmatic processes that take place when speakers of different varieties of L2 English come into contact. For Meierkord, a key difference between intranational and international contexts is that in the former interactions tend to take place in relatively stable communities, circumstances which are more propitious for the adoption of new features and the eventual emergence of new L2 varieties; for example, the nativised varieties of post–colonial societies. In international contexts, by contrast, lingua franca encounters tend to be more short-term, and there is therefore less opportunity for the emergence, adoption and stabilisation of new features. Accommodation, rather, is one of the more common pragmatic responses. These, however, are rough generalisations, for throughout the book an important motif is heterogeneity: heterogeneity in the varieties of English entering into contact, heterogeneity in speaker characteristics such as their level of English proficiency, and heterogeneity in the purposes and contexts of the encounters.