Elasticity = The ability of a solid to return to its original shape or form after being subject to strain.
i do not know its measurement
you are only talking about theoretical .. just give me one practical example?

well in my mind still gobs of questions arise ...
a interesting one :P
so why don't we use steel in our trousers or make a world most expensive trouser by using Diamond ?

"Elasticity is a measure of responsiveness. The responsiveness of behavior measured by variable Z to a change in environment variable Y is the change in Z observed in response to a change in Y. Specifically, this approximation is common:

elasticity = (percentage change in Z) / (percentage change in Y)

The smaller the percentage change in Y is practical, the better the measure is and the closer it is to the intended theoretically perfect measure."