Lingua francas are languages used for communication between individuals for whom they are not the first language. Based on empirical work throughout, the individual contributions to this volume address lingua franca communication from sociolinguistic as well as from conversation analytic perspectives, or place this form of communication within the wider context of foreign language teaching. The volume as a whole attempts to broaden the traditional view of lingua francas as languages employed by non-native speakers to serve specific, restricted communicative purposes only. Instead, it is demonstrated that lingua francas have gained a number of varied functions, and that they are employed by a heterogeneous group of speakers for whom they do not always have the same status of a second or foreign language. The papers reveal intriguing similarities in form across different lingua francas, but also point at significant differences. As a result, it is proposed that approaches to teach lingua francas as such need to be developed on the basis of empirical evidence.