Elasticity is define as the "quality sth has being able to stretch and go back to its original decoration". (Oxford advanced learners dictionary 6th edition) In Physics elasticity is defined as "the house of a substance that enables it to improve its length, volume, or condition in direct reaction to a force effecting such a big change and to recover its original form upon removing the force. " (dictionaryreference. com). Suppose that your employer allows you to work extra hours more after your contracted hours for extra pay by the end of the month, the amount of extra money you will earn at the end of the month will depend on how much more extra hours it is possible to work. Then how responsive you are to the offer is seen as elasticity. Therefore I am going to define elasticity as the way of measuring amount of responsiveness of any variable to extra stimulus.