Several components contribute to the usability of a system:
Learnability: How easy is it for users to accomplish basic tasks the first time they encounter the system? Efficiency: Once users have learned the system, how quickly can they perform tasks? Memorability: When users return to the system after a period of not using it, how easily can they re-establish proficiency? Errors: How many errors do users make, how severe are these errors, and how easily can they recover from them? Satisfaction: How pleasant is it to use the system?
