The document discusses the law of demand and elasticity of demand. It defines the law of demand as stating that, other things equal, demand increases as price decreases and decreases as price increases. It defines elasticity of demand as the percentage change in quantity demanded divided by the percentage change in price. It then defines price elasticity of demand, income elasticity of demand, and cross elasticity of demand. Finally, it discusses applications of the law of demand including price determination, government policy formulation, demand forecasting, and international trade. It also discusses uses of elasticity of demand in business for price strategy, marketing, and production.