How effectively and efficiently an individual user can achieve a specific goal through the use of an interface, product, or tool.
Five of the key criteria used to evaluate usability are learnability, efficiency, memorability, errors, and satisfaction.
5 quality components define usability:
- Learnability: How easy is it for users to accomplish basic tasks the first time they encounter the design?
- Efficiency: Once users have learned the design, how quickly can they perform tasks?
- Memorability: When users return to the design after not using it, how easily can they reestablish proficiency?
- Errors: How many errors do users make, how severe are these, and how easily can they recover from them?
- Satisfaction: How pleasant is it to use the design?