1. the functional relationship between the price of a given commodity and the quantity that buyers would be willing and able to purchase in a given market during a specified time period —note demand is typically expressed as either a mathematical equation (showing quantity demanded as a function of price) or as a curve showing price per unit plotted over quantity 2. the actual quantity of a commodity or service that buyers are willing to purchase in the market at a given price over a specified time period —see supplyThis definition last updated 10/25/2008