The cross-price elasticity of demand is a measure of how much the quantity demanded of one good responds to a change in the price of another good. when the price of a good changes, the quantity demanded of related goods also changes. Two goods are either substitute to each other or they are complement each other. If the price increase in one good (good X) causes consumers to use other good (good Y) in place of this good, we say that these two goods (X and Y) are substitutes for each other. Substitutes are goods that are generally used in place of one another. Concerning the substitute goods, a price increase in good X leads to quantity demanded of good Y to increase. Goods have also complementary relationship. Complements are goods that are typically used together