The amount of income that people have available to spend on goods and services.

The principle that, all other factors being equal, consumers will purchase (demand) more of a good at lower prices and less of a good at higher prices.

The natural decreases in the utility of a good or service as more units of it are consumed.

The situation that exists when quantity demanded changes greatly in response to a change in price.

The situation that exists when quantity demanded changes only slightly or not at all in response to a change in price.

A business's total income; sometimes called total receipts.

Consumers' tendency to substitute a lower-priced good for a similar, higher-priced one.

A product that purchasers use in place of another product, particularly if the price of the other product rises.

A good that is commonly used with another good and for which demand increases (or decreases) when the demand for the related good increases (or decreases).