What does the cross-price elasticity measures?

The concept of cross-price elasticity of demand is related to estimating, measuring, or quantifying the degree of relationship between price and quantity demanded in the case of related goods like substitutes and complementary. It basically measures the effect of change in the price of related goods like substitutes and complementary to the change in quantity demanded in proportionate terms. In the case of substitutes, the cross-price elasticity shows a positive value whereas in the case of complementary cross-price elasticity shows a negative value.