1. the functional relationship between the price of a given commodity or service and the quantity that sellers would be willing and able to sell in a given market during a specified time period —note supply is typically expressed as a mathematical equation (showing quantity supplied 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 offered by sellers in the market over a specified time period —see demandThis definition last updated 10/23/2008