Price elasticity of supply (PES) measures the responsiveness of the quantity supplied of a good to changes in its price. There are several types of PES including perfectly inelastic, elastic, perfectly elastic, and unitary elastic supply. Perfectly inelastic supply means quantity supplied does not change with price changes, while elastic supply means a small price change leads to a greater proportional change in quantity. Perfectly elastic supply occurs when a price change leads to an infinite quantity change. Factors affecting PES include time, resources, production costs, and product nature. PES can be calculated and is used to analyze how producers respond to price changes.