Usability

Usability is a discipline that assesses (quantitatively and qualitatively) how a product, service or system satisfies the following characteristics:

• Learnability: the system is easy to learn so users can start using it the first time without major issues.

• Efficiency: the system allows users to perform their tasks quickly.

• Memorability: the degree at which a user remembers how to perform a task with a system after a while not using it.

• Efficiency: the degree at which the users don't make mistakes while performing a task with a system; and if they do make mistakes, they are not fatal and it is easy for the user to recover from them.

• Satisfaction: the system is pleasant to use and leaves a positive impression after using it.

Usability is applied in the design processes or used for the evaluation and products or services improvement. Usability is not an abstract concept, but a very concrete one: studies the user performing an specific task, in a given context.