Usability engineering is a field that is concerned generally with human-computer interaction and specifically with making human-computer interfaces that have high usability or user friendliness. In effect, a user-friendly interface is one that allows users to effectively and efficiently accomplish the tasks for which it was designed and one that users rate positively on opinion or emotional scales. Assessing the usability of an interface and recommending ways to improve it is the purview of the Usability Engineer. The largest subsets of Usability Engineers work to improve usability of software graphical user interfaces (GUIs), web-based user interfaces, and voice user interfaces (VUIs).
Several broad disciplines including Psychology, Human Factors and Cognitive Science subsume usability engineering, but the theoretical foundations of the field come from more specific domains: human perception