A "requirement" is a specific need or condition that must be met for a project, product, or process to be successful. It outlines what is necessary to achieve a desired outcome, ensuring that all stakeholders have a clear understanding of expectations. Requirements can be functional, detailing what a system should do, or non-functional, describing how a system should perform. In various fields, such as software development or engineering, requirements serve as a foundation for planning and execution. They help guide the design, development, and testing phases, ensuring that the final result meets the needs of users and complies with relevant standards.