Answer:
Monopoly
A monopoly exists when a specific person or enterprise is the only supplier of a particular commodity. This contrasts with a monopsony which relates to a single entity's control of a market to purchase a good or service, and with oligopoly and duopoly which consists of a few sellers dominating a market.
Oligopoly
An oligopoly is a market form wherein a market or industry is dominated by a small group of large sellers. For example, it has been found that insulin and the electrical industry are highly oligopolist in the US.
Perfect competition
In economics, specifically general equilibrium theory, a perfect market, also known as an atomistic market, is defined by several idealizing conditions, collectively called perfect competition, or atomistic competition.
Imperfect competition
In economics, imperfect competition refers to a situation where the characteristics of an economic market do not fulfil all the necessary conditions of a perfectly competitive market, resulting in market failure.
Explanation:
A monopoly is a firm who is the sole seller of its product, and where there are no close substitutes. An unregulated monopoly has market power and can influence prices. Examples: Microsoft and Windows, DeBeers and diamonds, your local natural gas company.
Oligopoly arises when a small number of large firms have all or most of the sales in an industry. Examples of oligopoly abound and include the auto industry, cable television, and commercial air travel. Oligopolistic firms are like cats in a bag.
Agricultural markets are examples of nearly perfect competition as well. Imagine shopping at your local farmers' market: there are numerous farmers, selling the same fruits, vegetables and herbs. You can easily find out the prices for the goods, but they are usually all about the same.
Imperfect competition occurs when at least one condition of a perfect market is not met. Examples of imperfect competition include, but aren't limited to, monopolies and oligopolies.
The most common examples of imperfect competition are monopoly, monopolistic competition, and oligopoly.
