What is the primary function of a use case in UML?

A use case in Unified Modeling Language (UML) serves as a pivotal component in system design by detailing steps in a business process. It describes how users (or "actors") interact with the system to achieve specific goals, representing a sequence of actions or events that lead to an outcome. This function allows stakeholders to understand user interactions and the functional requirements of the system being developed.

By focusing on user perspectives and their interactions with the system, use cases help to uncover system requirements, identify potential issues in user experience, and refine the overall design process. They serve as a communication tool among various stakeholders, ensuring everyone has a clear understanding of how the system should behave in specific scenarios.

While outlining system architecture, representing entity relationships, and defining software requirements are important aspects of systems analysis, they do not encapsulate the primary role of a use case. The emphasis on detailing the steps in user interactions is what makes use cases a fundamental part of capturing requirements in a way that aligns with user needs.