Quantitative Methods. Yeeks

I had a class in Quantitative Methods this morning.....During the course of it, the professor came up with this question - "What is the term u use to denote the extent to which you can use a product- say a light bulb or a rocket?" Each of us tried to come up with some answers. My class has a majority of engineers and am a Zoology graduate. They came up with the right answer of course which happens to be Reliability! And my answer was life time or life expectancy!! No points for guessing....Goes to show how truly zoological I am!!!