‘Usability’ is about creating software that is effective (does what it’s supposed to do), efficient (quick and to-the-point) and makes the user satisfied. User experience (UX) goes a step further, aiming for lasting impressions, real emotions and the big picture. For creating great software you need to understand both the business context and the user’s perspective.
What others say:
Wikipedia says:
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.
Google starts with:
Quite simply, usability is making your site easy for your customers to find the exact information they need when they need it. …
www.searchenginewriting.com/glossary.shtmlA set of attributes that bear on the effort needed for use, and on the individual assessment of such use, by a stated or implied set of users. Learnability Understandability Operability
www.bigpedia.com/encyclopedia/ISO_9126the ease of use, learnability, efficiency, and error tolerability of a particular product.
www.utexas.edu/academic/diia/assessment/iar/glossary.php