This document discusses language as a complex adaptive system according to complexity theory. It provides background on complexity theory and how it explains complex systems. Key aspects of complex systems are that they emerge from interactions, are unpredictable, sensitive to initial conditions, and self-organize. Language learning is discussed as nonlinear and dynamic. Language itself is a complex system with interdependent subsystems at different levels and timescales. The document contrasts traditional, linear views of language with a complex systems perspective, noting language is constantly changing through use and difficult to predict.