In economics, one way that two or more goods can be classified is by examining the relationship of the demand schedules when the price of one good changes. This relationship between demand schedules leads to classification of goods as either substitutes or complements. Substitute goods are goods which, as a result of changed conditions, may replace each other in use (or consumption).[1] A substitute good, in contrast to a complementary good, is a good with a positive cross elasticity of demand. This means a good's demand is increased when the price of another good is increased. Conversely, the demand for a good is decreased when the price of another good is decreased. If goods A and B are substitutes, an increase in the price of A will result in a leftward movement along the demand curve of A and cause the demand curve for B to shift out. A decrease in the price of A will result in a rightward movement along the demand curve of A and cause the demand curve for B to shift in.