In general terms, elasticity is the amount of stretch that an object contains. It is property by virtue of which matter keeps its shape from deforming into another.
When an external force is applied to an object the size and shape of the object may change, for example, an appropriate force is applied to a spring can elongate it. If the force ceases to act the object may restore to its original size and shape. An object is said to be elastic if it restores its original size and shape. This property of an object is known as elasticity.
In economics, elasticity refers to the sensitivity of one variable to changes in a different variable. How much more of a product consumers will purchase when the price of that product falls is a specific example of economic elasticity.