Which of the following is not factual about supply and demand?

The statement that is not factual about supply and demand is the one indicating that supply refers to either the willingness or ability of potential sellers. In economic terms, supply specifically encompasses both the willingness and the ability of sellers to offer goods or services at different prices. Thus, it is essential that both components are included to accurately represent supply.

The remaining choices accurately describe aspects of supply and demand. Demand indeed reflects both willingness and ability to pay, which shows that consumers must not only want a good or service but must also have the financial means to purchase it. The characterization of a demand curve as representing the relationship between price and quantity demanded is also correct. It illustrates how, typically, as prices decrease, the quantity demanded by consumers increases, following the law of demand. Similarly, a supply curve correctly represents the relationship between price and quantity supplied, where generally higher prices motivate sellers to offer more of a good.

Overall, understanding the precise definitions and interactions between supply and demand greatly aids in analyzing market behavior and economic principles.