What is "imperfect competition"

In economic theory, imperfect competition is a type of market structure showing some but not all features of competitive markets.

Forms of imperfect competition include:

• Oligopoly, in which there are few sellers of a product.
• Monopolistic competition, in which there are many sellers producing highly differentiated products.
• Monopsony, where there are many sellers but only one buyer, and oligopsony, where there are many sellers but few buyers.