The usability factor
Let’s take usability first. My dictionary defines usability as the state or quality of being usable. Not too much help there. Usable, in turn, was defined as that can be used; fit; convenient, or available for use. Still not much help. As a generic software-oriented definition, we can probably say that usability is a set of conditions that supports the effective and efficient utilization of a tool, on its intended applications, to achieve a specified set of objectives.