This chapter examines vocabulary explanations during Swedish as a second language (L2) lessons for beginner learners in a primary school classroom, attended by 10- to 12-year-old children with immigrant backgrounds. It shows how teachers elaborated word meanings through short narratives and descriptions that demonstrated uses of words to students as prospective users. It argues that vocabulary-related explanations were dynamic activities in which teachers mediated not only linguistic forms but also culturally appropriate meanings and values, ways of thinking and behaving in new communities of practice, and provided affordances for shaping the lifeworlds and identities of the second language learners. The students’ responses reveal that, rather than simply appropriating the teachers’ norms and values, they engaged in a process of actively negotiating, disagreeing, and even resisting the teachers’ narrative exemplifications. The findings show how vocabulary explanations are a locus for socializing children into appropriate language use and cultural membership in the target-language community, attesting to the negotiated and, at times, resistant process of becoming an L2 speaker.