Again, in both monopolistic and oligopolistic market structures there is no freedom of entry and in both cases the companies involved have some control over prices. In monopolistic market structures and perfect competition, we have many sellers and buyers. In monopolistic market structures and perfect competition, we also have easy access and therefore have fewer barriers to entry and exist. When comparing market structures, the monopoly structure is different from others in that it has only one seller or producer. It is also a monopolistic structure where a single seller enjoys the profits alone. Oligopoly differs from other structures in that there are only sellers who can cooperate together, because forming cartels means they are willing to communicate to control the price of the product. Perfect competition market structure is different from others because it only occurs when sellers and buyers have perfect knowledge of the market.