Dissecting the ‘E’ and the ‘I’ in EMI through a Bakhtinian lens: Monoglossic versus heteroglossic meanings and practices across academic disciplines

English-medium instruction (EMI) has been implemented in numerous countries, including Vietnam. EMI has thus been extensively researched, yet more attention should be paid to disciplinary differences and their influences on the perceived meanings and classroom practices of EMI. Therefore, this paper is aimed at exploring the perceived meanings of the ‘E’ and the ‘I’ in EMI as well as EMI lecturers' linguistic and pedagogical practices in light of disciplinary differences–that is, in two courses: maths and business. Theoretically, it drew upon Bakhtin's theory of dialogism and its fundamental notions of monoglossia and heteroglossia ; methodologically, it drew upon triangulation of participant observation and interview to collect data. The collected data were then analysed by means of thematic analysis. Data analysis indicated disciplinary differences regarding the correspondence between a terminology and its interpretation(s). Consequentially, in the maths course, the perceived meanings and classroom practices of both the ‘E’ and the ‘I’ are monoglossic. In contrast, in the business course, the perceived meanings and classroom practices of both the ‘E’ and the ‘I’ are heteroglossic. Thus, the implication is that the revealed discrepancies should be taken into account in the formation and implementation of EMI(-related) policies and professional development programmes and/or courses for pre-service and in-service EMI lecturers. Future studies should observe more courses across academic disciplines in various educational settings as well as involving a greater number of interview participants to contribute to a richer understanding of EMI.