1. Introduction: A Transdisciplinary Framework of SLA 2. L2 knowledge is Complex and Dynamic 3. L2 Knowledge Is a Repertoire of Diverse Semiotic Resources 4. L2 Learning Is Situated, and Attentionally and Socially Gated 5. L2 Learning Is Mediated and Embodied 6. L2 Learning Is Mediated by Learners’ Social Identities 7. L2 Learning Is Mediated by Motivation, Investment, and Agency 8. L2 Learning Is Mediated by Literacy and Instructional Practices 9. L2 Learning Is Mediated by Language Ideologies