This paper discusses the idea that language should be thought of as a complex adaptive system (CAS). A CAS is an open system that is made up of many individuals and types of individuals that all interact in various and complex ways, and that is in a constant state of flux. Firstly, I will briefly introduce four general examples of CAS; ecosystems, the solar system, economies, and traffic networks. I will then generalise some of the characteristics that they have in common. Finally, I will discuss how these characteristics apply to language as a CAS, and what the implications of that are for us as teachers and researchers.