| # of Firms | Product Diff. | Entry/Exit | |
| Perfect Competition | Many | None | Free |
| Monopoly | One | None | Highly Restricted |
| Monopolistic Competition | Many | Significant | Free |
| Oligopoly | Few | Some | Restricted |   |
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You may recall the table to the left showing the primary characteristics that define the four main industrial structures that we will study. In this section we will concentrate on Monopoly. As you no doubt already know, a monopoly is an industry comprised of only one firm. | ||||||||||||||||||||||||