Under monopoly there is only one seller of a particular good for which there are no reasonably close substitutes. Therefore the firm is the industry and faces the negatively sloped industry demand curve for the commodity. As a result, in order to sell more of the commodity, the monopolist must lower its price. In fact, a monopolist can sell additional output only if it reduces prices. The size of this deadweight loss is approximated by the triangle measuring lost consumer and producer surplus because of this underproduction.
Monopolies often charge different prices for the same product.
This is called price discrimination when it occurs for reasons unrelated to costs. If these two conditions are hold, the price discriminator will sell the good at a higher price to the group with the lower elasticity of demand. 3- Easy entry or exit exists in the long run. By services provided by the seller's 3-By the physical quality of the good. By the subjective image formed by consumers about the good.