200 DOI: 10.4324/9781003177579-17 Introduction Language socialization (LS) research examines the concurrent development of linguistic and cul- tural knowledge through mediated social experience. Increasingly, LS research is being conducted in multilingual contexts, both inside and outside of classrooms, where second language (L2) develop- ment is one of the expected outcomes of interaction. (We use the term L2 generically to refer to a foreign, second/additional, or heritage language.) Other goals often include the transmission, uptake, or contestation of linguistic ideologies and social values, membership in a real or desired community mediated by the L2, particular affective dispositions, and other forms of knowledge that are learned and expressed at least in part through languages (L1, L2, Lx) and other semiotic systems (Duff & May, 2017; Duff & Talmy, 2011). In this chapter, we frst describe the theoretical underpinnings of LS and the main research meth- ods or approaches used in studies that are either explicitly or implicitly framed as LS. We then re- view and illustrate through selected sample studies how research has analyzed oral and multimodal discourse to demonstrate L2 socialization processes and (in some cases) outcomes. We examine re- search situated within classrooms and other less formal settings, such as dormitories, where multilin- gual students engage in discursive events and interactions with teachers and peers using their diverse linguistic repertoires and multimodal/embodied resources to develop their L2 profciency as well as other competencies and dispositions. We then discuss how such interactions and discourse contribute to participants’ L2 development and their understandings of local cultural ideologies connected with the L2 and of themselves. Finally, we conclude with a discussion of the contributions of LS studies to SLA, implications for educators, and promising directions for future research in this area. Overview of second language socialization research: Theoretical underpinnings The frst generation of research on LS in the 1980s focused primarily on children’s frst language (L1) development and use within families and communities. Often the linguistic focus was L1 pragmatics, such as requesting and shaming behaviors or other common routines of sociolinguistic signifcance (Schieffelin & Ochs, 1986). Since the early 1990s, the scope of LS research has expanded substan- tially (Duff & Hornberger, 2008; Duff & May, 2017; Duranti et al., 2012). In particular, there has been greater attention to the assisted development of linguistic/discursive and cultural knowledge and 16 LANGUAGE SOCIALIZATION, DISCOURSE, AND SECOND LANGUAGE RESEARCH Patricia A. Duff and Masaru Yamamoto