Income Elasticity: Income elasticity measures the responsiveness of demand for a good or service to changes in income. It indicates whether a good is normal (positive income elasticity) or inferior (negative income elasticity).
Substitutes: Substitute goods are products that can be used in place of each other. When the price of one substitute increases, the demand for the other substitute increases.
Complements: Complementary goods are products that are typically consumed together. When the price of one complement increases, the demand for the other complement decreases.