That quality of a system that makes it easy to learn, easy to use and encourages the user to regard the system as a positive help in getting the job done. User A person who uses a system to perform a business function. georgetown.edu
Usability is critical to the successful adoption of any application. When information and interfaces are presented in a clear, consistent and coherent manner, users can focus on the task at hand, instead of spending time and energy trying to make the application work.
Usability ensures that an application works the way it should, both in terms of technological effectiveness and user comfort.
The effort needed for use, and for individual assessment of such use, by a stated or implied set of users.