The role of a user interface (UI) in software design is to facilitate user interaction with a system or application. UI encompasses the visual elements, layout, and organization of menus and buttons that users engage with. A well-designed UI enhances usability by providing clear navigation and intuitive controls, which can lead to increased user satisfaction and retention. Effective UI design focuses not only on aesthetics but also on the overall user experience, ensuring that the software is both functional and enjoyable to use.