In a blog post, Justin Mifsud discuss the terms usability and user experience, highlighting their differences and more importantly the relationship that exists between them.
“Usability is a narrower concept than user experience since it only focuses on goal achievement when using a web site. By contrast, user experience is a “consequence of the presentation, functionality, system performance, interactive behaviour, and assistive capabilities of the interactive system”. This essentially means that user experience includes aspects such as human factors, design, ergonomics, HCI, accessibility, marketing as well as usability. An alternative way to look at this relationship is by subdividing user experience into utility, usability, desirability and brand experience. “