Despite different epistemologies and assumptions, all theories in second language (L2) acquisition emphasize the centrality of context in understanding L2 acquisition. Under the assumption that language emerges from use in context, the cognitivist approach focuses on distributions and properties of input to infer both learning objects and process of acquisition. The interactionist approach views context more narrowly by analyzing how a particular linguistic item is attended and processed during a task-based interaction, and how it becomes intake as learning outcomes. For socially-oriented theories such as the sociocultural theory and language socialization, learning is fundamentally situated in context. Through mediated participation in learning as social practice, learners come to appropriate linguistic knowledge. Context is also fundamental in the complex, dynamic systems theory, which views learning as a non-linear, adaptive process emerging through an interaction of resources and individuals within a given context. All of these theories give the central power to context to describe and explain L2 learning. Context serves as the site where acquisition is examined. Context also helps explain the process and outcomes of acquisition.