1.2.12 - Define the term usability.

How easy a system is to learn and use.

1) Learnability - how easy it is for users to accomplish basic tasks the first time they encounter a system. 2) Efficiency - once users have learned a system, how quickly they can perform tasks. 3) Memorability - when users return to a system after a period of time not using it, considering how easily they can re-establish they can re-establish proficiency. 4) Errors - the number, severity and how easy it is to recover from errors a user makes a system. 5) Satisfaction - how comfortable and pleasant it is to use a system.

Designing and arranging things that people and other things interact with as efficiently and safely as possible.

The ability of people to access and benefit from a system, taking special consideration of disability or special needs.