Book excerpt: Sociocultural research has long recognized the necessity of sustained interpersonal interaction for language development. However, less is known about the underlying relationships that promote language acquisition and their relevance for language classrooms. Presenting cutting-edge research on social networks and their applications in language teaching, this book explores the relationships that mediate language learning in and out of classrooms. Highlighting the complexity of language in multilingual contexts, chapters engage social network analysis to understand the role of instructional practices, socialization, motivation, language status, online communications technology, and language policies in the development of social resources for language learning. Discussing popular language teaching frameworks such as translanguaging, Social Networks in Language Learning and Language Teaching provides a nuanced account of the influences of social context on language learning, exploring classroom applications and pointing the way to a robust research agenda.