Drawing on theories from Applied Linguistics research, this doctoral dissertation brings together European perspectives on "language," "identity," and "voice" in an examination of English as the international language of science (EILS). Using the theoretical frame of Dynamic Systems Theory (DST), each of the chapters adopts a different perspective to examine EILS. At the macro-level, I conduct a comparative Critical Discourse Analysis (CDA) of English as a lingua franca discourse in the published declarations and communications of the European Higher Education Area (EHEA) and the European Research Area (ERA). The analysis adds nuance to claims that the EHEA has a disregard for language related matters and uncovers intra-institutional conflicts in how language is conceptualised between actors and across portfolios in the European Union (EU). At the meso-level, I use the lens of Conversational Analysis to enrich understandings of how European research scientists construct linguistic and disciplinary identities through turns-at-talk in a series of semi-structured interviews. The analysis emphasises the importance of the research interview's interactional features, which are often ignored in more dominant approaches to interview in English for Academic Purposes (EAP) research. Finally, at the micro level, a Usage-Based Linguistics (UBL) study reveals new insights into the development of a European research biologist's authorial voice across timescales and contexts. In particular, the study highlights the importance of discourse context in the analysis of voice features. In sum, this doctoral dissertation contributes to an important and productive site of scholarly debate by adopting epistemological approaches that foreground the importance of interaction and context in understanding language as a social practice. It provides original perspectives on the conceptualisation of language, the construction of identity, and the development of voice in the dynamic and complex system that is EILS. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://bibliotheek.ehb.be:2222/en-US/products/dissertations/individuals.shtml.]