In the analysis of communicational practices ¿ whether in the form of audience, audience, consumers, users, recipients, participants, spectators ¿ there is an imprecision of terms and occurrences that leaves room for terminological and theoretical indecision. Hence the desire to clarify the contours of the notion of public, while relying on empirical material, and to examine its multiple transformations. Thanks to a collective interdisciplinary program, researchers in information and communication sciences and in language sciences from the Center for Research on Mediations of the University of Lorraine have studied the conditions of production and diffusion of information and knowledge, the attitudes and behaviors of the public, the mechanisms of intercomprehension or of communicational blockages and the weight of technological factors in mediations. These issues are addressed using methods that combine sociological surveys, targeted ethnographic studies, experiments, and corpus analyses. They are applied to a variety of fi elds, extending work that has already been done, but also shaking up certain results. This book gathers a selection of signifi cant studies around four sections: the concept of public space; the relationship to the digital; innovations in the fi eld of health; the relationship to writing in the cultural sector.