Chapter 4 examines the situatedness of communicative practices to discuss the central role of languages in the dissemination of scientific knowledge. The concept of ‘fluid societies’ and Blommaert’s ‘sociolinguistics of mobility’ paradigm are used to propose a timely definition of academic and research settings as ‘fluid communities’ that engage in translingual and multilingual genre-mediated interactions. A critical review of the status and functions of English in the language ecology of such interactions introduces some reflections on language-related aspects – languaging practices, processes of language macroacquisition and coalescence of languages – that intersect with generified activity. Corpus and ethnographic (survey) data are used to describe ‘glocal’ and ‘translocal’ language use, language variation and change in and across genres. In contesting the monolingual habitus and foregrounding the plurilingual realities, the chapter closes with some final thoughts on the fact that ‘languages are still a major barrier to global science’.