Software reuse is the practice and systematic methodology of leveraging existing software artifacts, such as code, designs, documentation, and test cases, in the creation of new software systems. As a significant research area and engineering approach, it investigates the principles, processes, and tools necessary for effectively identifying, classifying, adapting, integrating, and managing these reusable assets. The concept is fundamentally characterized by the strategic utilization of pre-existing, validated components to achieve improvements in development efficiency, cost reduction, time-to-market acceleration, and system quality and reliability.