In economics, supply an demand describes market relations between prospective sellers and buyers of a good. The supply and demand model determines price and quantity sold in a market. This model is fundamental in microeconomic analysis, and is used as a foundation for other economic models and theories. It predicts that in a competitive market, price will function to equalize the quantity demanded by consumers, and the quantity supplied by producers, resulting in an economic equilibrium of price and quantity. The model incorporates other factors changing equilibrium as a shift of demand and/or supply.