The article "Complex Systems and Applied Linguistics" by Lynne Cameron and Diane Larsen-Freeman introduces complexity theory as a framework for understanding systems in applied linguistics. The authors emphasize that change and heterogeneity are central to complexity theory and its resonance with applied linguistics systems. They explain the principles of complexity theory, drawing on work from biology, psychology, and social sciences, and discuss how these principles can be applied to various levels and scales of systems. The article highlights that viewing applied systems as complex, adaptive, and dynamic opens up new ways of conceptualizing properties and activities, enabling new questions about language use, learning, and teaching. It also demands new methods for investigating behavior and development. The authors provide examples of complex systems in language and its evolution, language development, discourse, and the language classroom, illustrating how complexity theory can provide a more nuanced and dynamic perspective on these areas. In the language classroom, a complex systems perspective emphasizes the dynamic and evolving nature of language, the importance of interaction across interconnected levels and timescales, and the need for teachers to manage the dynamism and complexity of the target language. The article concludes by discussing research techniques compatible with complex systems approaches, including computer simulation and modeling, and outlines methodological principles for researching language and language development.The article "Complex Systems and Applied Linguistics" by Lynne Cameron and Diane Larsen-Freeman introduces complexity theory as a framework for understanding systems in applied linguistics. The authors emphasize that change and heterogeneity are central to complexity theory and its resonance with applied linguistics systems. They explain the principles of complexity theory, drawing on work from biology, psychology, and social sciences, and discuss how these principles can be applied to various levels and scales of systems. The article highlights that viewing applied systems as complex, adaptive, and dynamic opens up new ways of conceptualizing properties and activities, enabling new questions about language use, learning, and teaching. It also demands new methods for investigating behavior and development. The authors provide examples of complex systems in language and its evolution, language development, discourse, and the language classroom, illustrating how complexity theory can provide a more nuanced and dynamic perspective on these areas. In the language classroom, a complex systems perspective emphasizes the dynamic and evolving nature of language, the importance of interaction across interconnected levels and timescales, and the need for teachers to manage the dynamism and complexity of the target language. The article concludes by discussing research techniques compatible with complex systems approaches, including computer simulation and modeling, and outlines methodological principles for researching language and language development.