A brief history of known tries to define usability. All information belongs to the specific party referenced.
linkISO 9241-11:2018: Usability
The extent to which a system, product or service can be used by specified users to achieve specified goals with effectiveness, efficiency and satisfaction in a specified context of use.
Usability is relevant to:
- regular ongoing use, to enable users to achieve their goals effectively, efficiently and with satisfaction;
- learning, to enable new users to become effective, efficient and satisfied when starting to use a system, product or service;
- infrequent use, to enable users to be effective, efficient and satisfied with the system on each reuse;
- use by people with the widest range of capabilities;
- minimizing the risk and the undesirable consequences of use errors; and
- maintenance, in that it enables maintenance tasks to be completed effectively, efficiently and with satisfaction.
linkDefinition of Usability as per Nielsen & Norman
Usability is a quality attribute that assesses how easy user interfaces are to use. The word “usability” also refers to methods for improving ease-of-use during the design process.
Usability is defined by 5 quality components:
- 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 a period of not using it, how easily can they reestablish proficiency?
- Errors: How many errors do users make, how severe are these errors, and how easily can they recover from the errors?
- Satisfaction: How pleasant is it to use the design?
linkUsability requirements for different aspects of the user experience
- Effective: How completely and accurately the work or experience is completed or goals reached
- Efficient: How quickly this work can be completed
- Engaging: How well the interface draws the user into the interaction and how pleasant and satisfying it is to use
- Error Tolerant: How well the product prevents errors and can help the user recover from mistakes that do occur
- Easy to Learn: How well the product supports both the initial orientation and continued learning throughout the complete lifetime of use