Usability is the ease of use and learnability of a human-made object. The object of use can be a software application, website, book, tool, machine, process, or anything a human interacts with, in other words Usability means making products and systems easier to use, and matching them more closely to user needs and requirements.
The international standard, ISO 9241-11, provides guidance on usability and defines it as:
“The extent to which a product can be used by specified users to achieve specified goals with effectiveness, efficiency and satisfaction in a specified context of use.”
The primary notion of usability is that an object designed with a generalized users’ psychology and physiology in mind is, for example:
- More efficient to use—takes less time to accomplish a particular task
- Easier to learn—operation can be learned by observing the object
- More satisfying to use
Usability consultant Jakob Nielsen and computer science professor Ben Shneiderman have written (separately) about a framework of system acceptability, where usability is a part of “usefulness” and is composed of:
- 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 re establish 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?
Usability should not be confused with ‘functionality’, however, as this is purely concerned with the functions and features of the product and has no bearing on whether users are able to use them or not. Increased functionality does not mean improved usability!Again, these are already know facts, but I faced this in recent times, so thought of jotted it down.