Usability is the ease with which users get the feel of the system and make productive usage of the processes. It is frequently emphazied in relation to the interfaces of the system; it can as well be applied to any device, tool or rich application.

This process involves the following key aspects:

• Efficiency: How efficiently can a end user perform a task once they have learned the UI design
• Learnability: Ease for end users to accomplish primitive processes the first time they encounter the UI.
• Memorability: When users return to the system after a time frame, how quickly can they re-establish expertise
• Errors: How many errors do end users make, how severe are these, and how easily can they recover from these errors?
• Satisfaction: How pleasing is it to use the system