Under perfect competition, Elasticity of Demand is perfectly elastic, i.e. ${{E}{d}}$ = $\infty $. This indicates that unlimited quantity can be sold at the prevailing price.
On the other hand, under monopolistic competition, the Ed is greater than one, i.e. ${{E}{d}}$ > 1. This means that the responsiveness of demand is high with change in price. A small change in price will bring greater change in demand due to existence of many firms in the market, selling close substitute goods.