User interface (UI) design plays a crucial role in software usability by determining how users interact with applications. A well-designed UI ensures that software is intuitive and user-friendly, making it easier for individuals to navigate and accomplish tasks. Elements such as layout, color schemes, and iconography significantly impact user experience. Good UI design improves accessibility and reduces learning curves, which can enhance overall productivity. In competitive markets, effective UI design can differentiate a product and increase user retention, emphasizing its importance in achieving business goals.