Elasticity of substitution is a measure of how easily something is able to be substituted with something else. It is often used in marketing and economics. A product has a low elasticity if it is unable to raise its price because similar products (substitutes) are available. A product that is unique is able to charge higher prices because there are not as many choices. For example, in a fish market, there are many fishermen selling many fish. The price is not elastic because there is competition between many suppliers of fish.