In HCI and computer science, usability refers to the elegance and clarity with which an application or web site is designed.
The term is also commonly used in the context of the efficient design of consumer electronics products, knowledge transfer objects (such as cookbooks), and a huge range of other mechanical objects such as door handles, hammers, paper clips, can openers, and so on.
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".
Usability - whether of products, systems or services - is concerned with three fundamental things:
- Effectiveness - can users do what they want and need to do?
- Efficiency - how much effort do users require in order to be effective?
- Satisfaction - what do users think about the ease of use?
In turn, these three fundamental things are crucially affected by:
- The users - who are they, what do they know, and what can they learn?
- Their goals - what are the users trying to do?
- The context of use - where and how is the product, system or service being used?