Modularity is a principle concerning the organization of complex systems into distinct, self-contained units. This concept investigates the structure and behavior of systems composed of loosely coupled, highly cohesive components. Key characteristics include the decomposition of a system into modules with defined interfaces, internal autonomy, and potential for independent modification or replacement. Its significance lies in enabling complexity management, facilitating design efficiency, promoting reusability and evolvability, and enhancing robustness and understanding of system dynamics across diverse disciplines such as engineering, biology, and cognitive science.