demand and supply
Definition
Economic forces fundamental to the price mechanism in a free market system. They determine the price of a good or service offered, and are in turn determined by the price obtainable. It is a largely self-regulatory mechanism generally resulting in market equilibrium where products demanded at a price are equaled by products supplied at that price.
News containing the term demand and supply
http://www.businessdictionary.com/definition/demand-and-supply.html

