This document discusses elasticity of demand, including its meaning, types, and methods of measurement. There are three types of elasticity: price elasticity, income elasticity, and cross elasticity. Price elasticity measures the responsiveness of demand to changes in price. Income elasticity measures the change in demand from changes in consumer income. Cross elasticity measures the change in demand of one good from price changes in related goods. Methods for measuring price elasticity include the point method, percentage method, and arc method. Factors like substitutes, income level, and proportion of expenditure influence a good's elasticity. Understanding elasticity is important for setting prices, fiscal policy, and international trade.