Of -opolies and men.
Monopolies are markets where there is only one seller (monopolies can also refer to the single seller directly). These usually can happen because of a variety of situations.
Natural monopolies occur when the costs for making products for an industry are lowest when there is only one seller. It is the logical conclusion to a market situation where competition would be negative overall. Such monopolies include many public infrastructures, like electricity and water supplies. These monopolies result in lower costs for producers, which could translate to consumers through lower prices. However, it stops consumers from being able to choose between competing businesses for a good deal.
Geographic monopolies occur when there is only one producer in an industry within an area. These usually occur in a small area, and include many, if not all, "small-town" businesses, which are usually the only ones of their kind in a local area. These are usually borne of demand too small to warrant more than one producer, so competition is not "needed" as much; this helpfully lessens the disadvantages of little/no competition.
Technological monopolies occur when only one producer has control over methods of production or control of a technology itself. These include technological patents. Patents can encourage technological development because of a guarantee of exclusive rights, but can repress development through it as well by not allowing others to change and improve the technologies. They can also lead to an unhealthy dependency on one producer.
Government monopolies are monopolies that occur through the government's efforts; more specifically, when the government controls the single producer, or authorizes the only producer to be the only producer. These can tie into many natural monopolies, which are overall a good thing. However, government businesses can become price makers, disrupting the market equilibrium.
Oligopolies are market structures where only a few large firms control a very large portion of the market. We have many oligopolies in the modern world, from gas companies to chicken producers. Due to the lack of a multitude of serious competitors, producers can afford to create higher prices. However, the competitors that do exist force businesses to consider them in their decisions, installing caution many of the actions of businesses. Oligopolies overall are a middle ground between near-perfect competition and monopolies.
Monopolist competition is the strange child of monopoly and near-perfect competition. It has elements of both. It has somewhat easy entering and exiting of markets, and competition between businesses over prices, which are definitely good. There is also product differentiation, which is a deviation from near-perfect competition (which uses standardized and easily substitutable products). Some examples would be clothing stores, which can offer similar but not the same products. These can moderately lower prices.
Characteristics, advantages, disadvantages, examples, sources
Monopolistic competition, oligopoly, monopolies (natural, geographic, technological, and government)