Usability is a term used to denote the ease with which people can employ a particular tool or other human-made object in order to achieve a particular goal. Usability can also refer to the methods of measuring usability and the study of the principles behind an object's perceived efficiency or elegance.

In human-computer interaction and computer science, usability usually refers to the elegance and clarity with which the interaction with a computer program or a web site is designed. The term is also used often in the context of products like consumer electronics, or in the areas of communication, and knowledge transfer objects (such as a cookbook, a document or online help). It can also refer to the efficient design of mechanical objects such as a door handle or a hammer.

Introduction

The primary notion of usability is that an object designed with the users' psychology and physiology in mind is, for example:

• More efficient to use—it takes less time to accomplish a particular task
• Easier to learn—operation can be learned by observing the object
• More satisfying to use

Complex computer systems are finding their way into everyday life, and at the same time the market is becoming saturated with competing brands. This has led to usability becoming more popular and widely recognized in recent years as companies see the benefits of researching and developing their products with user-oriented instead of technology-oriented methods. By understanding and researching the interaction between product and user, the usability expert can also provide insight that is unattainable by traditional company-oriented market research. For example, after observing and interviewing users, the usability expert may identify needed functionality or design flaws that were not anticipated. Method called "contextual inquiry" does this in the naturally occurring context of the users own environment.

In the user-centered design paradigm, the product is designed with its intended users in mind at all times. In the user-driven or participatory design paradigm, some of the users become actual or de facto members of the design team.

The term user friendly is often used as a synonym for usable, though it may also refer to accessibility.

There is no consensus about the relation of the terms ergonomics (or human factors) and usability. Some think of usability as the software specialization of the larger topic of ergonomics. Others view these topics as tangential, with ergonomics focusing on physiological matters (e.g., turning a door handle) and usability focusing on psychological matters (e.g., recognizing that a door can be opened by turning its handle).

Usability is also very important in website development. According to Jakob Nielsen, "Studies of user behavior on the Web find a low tolerance for difficult designs or slow sites. People don't want to wait. And they don't want to learn how to use a home page. There's no such thing as a training class or a manual for a Web site. People have to be able to grasp the functioning of the site immediately after scanning the home page—for a few seconds at most."