What does the term usability mean?

I figured it might make sense to start my journey by defining the term usability. After all, one of the first steps to learning anything is to be able to define what it is you are attempting to learn.

I have seen a number of great definitions of the term by people far brighter than me. Like this one from Jakob Nielsen,

“Usability is a quality attribute that assesses how easy user interfaces are to use. The word “usability” also refers to methods for improving ease-of-use during the design process.” http://www.useit.com/alertbox/20030825.html

Though Mr. Nielsen’s definition correctly (in my opinion) uses the general term, “user interfaces”, most definitions seem to define usability through the lens of its role in “electronic” user interfaces. For me, a definition that restricts the term to websites and software applications doesn’t fit with my understanding. Sure, Google is easy to use, but so is my microwave.To fully internalize it, I have attempted to create my own definition. A definition that represents my understanding of the term usability. My definition of usability is:

Usability is the quantitative and qualitative measurement of how easy any particular thing is to use by humans-or maybe more accurately, that thing which is quantitatively and qualitatively measured.

I use the terms “quantitative” and “qualitative”, because, though the study of usability is certainly a science that requires hard facts and stats, such as those collected by Mr. Nielsen and his partners, it is also an art. It is something that is felt. It is felt by each person that interacts with some thing and decides that the interaction was frustrating or pleasantly simple.