Usability is a crucial aspect of UX/UI design, as it refers to how easily and effectively users can interact with a product or service. When a design is highly usable, it means that users can complete their goals quickly and efficiently, without experiencing frustration or confusion. There are several reasons why usability is important in UX/UI design:

1. Improved user satisfaction: When a design is usable, users are more likely to enjoy using the product or service, which can lead to increased satisfaction and loyalty.
2. Increased efficiency: Highly usable designs allow users to complete tasks faster and more efficiently, which can save them time and effort.
3. Reduced errors: Usable designs are less prone to errors, as they are easy to understand and navigate. This can reduce the risk of user frustration and mistakes, and can lead to a better overall user experience.
4. Increased conversion rates: When a design is usable, users are more likely to complete the desired actions, such as making a purchase or filling out a form. This can lead to increased conversion rates and revenue.
5. Competitive advantage: In today's crowded digital landscape, usability can be a key differentiator for businesses. Companies with highly usable products and services are more likely to stand out and be successful in their markets.

To ensure usability in UX/UI design, designers should focus on creating intuitive and logical layouts, using clear and consistent language, and making sure that the design is responsive and accessible to all users. It’s also important to test designs with real users to get feedback and identify any usability issues. By prioritizing usability in the design process, designers can create products and services that are easy, efficient, and enjoyable for users.