Which concept describes the ability of software to be learned, understood, and attractive to users under specified conditions?

Usability refers to the extent to which software can be effectively learned and understood by users, as well as how appealing it is to them under defined conditions. This concept encompasses various aspects of user experience, including the ease of learning the system, the efficiency with which users can achieve their goals, and the satisfaction they derive from using the software. Ensuring high usability is essential in agile development, where user feedback and iterative improvements are crucial for creating software that meets user needs.

The other options do not address this broad scope of user interaction as effectively. Testability relates to how easily software can be tested to ensure it meets quality standards. Performance pertains to how well software executes its tasks, especially under load or time constraints. Traceability involves the ability to track the origin and evolution of requirements throughout the development process. While all these aspects are important for software development, they do not specifically capture the focus on learning, understanding, and user attractiveness that usability embodies.