Pure Competition: A market structure with many competitors selling virtually
identical products. In today's U.S. economy, examples of pure competition have
virtually disappeared. The example of agricultural products probably comes the
closest.
Monopolistic Competition: A market structure with many competitors selling
differentiated products. Producers have some control over the price of their wares,
depending on the value that they offer their customers. And new producers can fairly
easily enter categories marked by monopolistic competition. Examples might include
the clothing industry and fast food establishments.
Oligopoly: A market structure with only a handful of competitors selling products that
are either similar or different. The retail gasoline business and the car manufacturing
industry, for example, are both oligopolies. Another example might include the soft
drink industry.
Monopoly: A market structure with just a single producer completely dominating the
industry, leaving no room for any significant competitors. Monopolies usually aren't
good for anyone except for the company that has control, since without competition
there isn't any incentive to hold down prices or increase quality and choices. Because
these undesirable drawbacks can harm the economy, most attempts to monopolize
markets in the United States are illegal. However, the government does allow
monopolies to operate in certain special cases. The classic example is a natural
monopoly, such as a cable television system, water company, or electric utility. The
government also fosters temporary monopolies when it grants patents or copyrights.