Which best describes a demand function?

A demand function is a mathematical representation that captures the relationship between the price of a good and the quantity demanded by consumers. It typically shows how much of a product consumers are willing to purchase at different price levels, with all else being constant. This is fundamentally about illustrating consumer behavior in response to price changes, which is succinctly expressed through a demand curve when plotted graphically.

The correct description indicates that a demand function can express this relationship quantitatively, often in the form of an equation that shows quantity demanded as a function of price. It does not encompass a list of all factors affecting demand, such as consumer income or tastes, nor does it directly relate to the supply of goods or measures of consumer satisfaction.

Thus, while a demand function does relate to how quantity demanded varies with price, it is not about listing factors or measuring quantities in the market; rather, it focuses on the specific relationship between price and quantity demanded, which makes it an essential concept in microeconomics.