Oligopoly

An oligopoly is an imperfect monopoly.

Because of the ease of collusion, particularly price fixing, duopolies and oligopolies easily produce outcomes as bad for the general public as outright monopolies.

For the sheep are falling into few and powerful hands; and these, if they have not a monopoly, have at least an oligopoly, and can keep up the price.

[Thomas] More makes an antithesis between monopolium and oligopolium. We have ‘monopoly,’ but not ‘oligopoly’ (the sale by a few), and so cannot preserve the point of the sentence.

An embarrassing infelicity is the use of Russianised consonants, where for six of the consonants, an additional set is made by supersigns, representing the letter h. […] The specialist offices have it all to themselves; not a 'monopoly’, but an ‘oligopoly’, if we may coin the term.

The major difference between pure and differentiated oligopoly cases is that in pure oligopolies less "shock" is needed to alter the organization of the market.

Although the power source had shifted from the king's near monopoly into an elite oligopoly, the masses were still afflicted when they sought wood fuel. But through the oligopoly, charcoal fuel proliferated throughout London's trades and industries. By the 1200s, brewers and bakers, tile makers, glassblowers, pottery producers, and a range of other craftsmen all became hour-to-hour consumers of charcoal. This only magnified the indispensable nature of the oligopolists.

By the late 1930s, however, the major film companies had consolidated their status as vertically-integrated oligopolies that dominated movie production, distribution and exhibition.

Not only does the tech oligopoly seamlessly record our preferences, habits, and choices, it also uses that data to guide our future choices, rendering us increasingly useful to the tech companies and useless to ourselves.

Depending on whether they are collusive or competitive, oligopolies can be more like monopolies or more like perfect competition, respectively, as a Khan Academy video explains.