Also known as: ease of use
Usability is the degree to which a product or system can be used by specified users to achieve specified goals with effectiveness, efficiency and satisfaction in a specified context of use (ISO 9241-11).
Usability is not the same as user experience (UX). UX is broader, encompassing all aspects of a person's interaction with a product, including aesthetics, emotions, and brand perception. Usability is a measurable attribute of a system: can users actually accomplish what they set out to do?
The ISO 9241 standard breaks usability into three components:
- Effectiveness: can the user achieve their goals at all?
- Efficiency: how much effort, time and resources does it take?
- Satisfaction: how comfortable and pleasant is the experience?
Good usability matters most in safety-critical domains like aviation, medicine, and nuclear power, where usability failures can kill people. But it matters everywhere — poor usability wastes time, causes frustration, and excludes users with disabilities.
Related terms: User Experience, ISO 9241, Human-Centred Design
Discussed in:
- Chapter 1: Introduction: What Is Usability? — Introduction
Also defined in: Textbook of Usability