In a perfectly competitive market, the individual firm is a price taker, meaning that it has no control over the market price. Therefore, the demand curve for an individual firm is perfectly elastic, which is represented by a horizontal line.

A monopoly is a market structure in which there is only one seller of a particular product or service. This gives the monopolist complete control over the market and allows them to set prices and output levels without competition.

In an oligopoly, firms are interdependent because their decisions regarding price, output, and other strategic variables directly impact the profits of other firms in the market. This interdependence leads to complex interactions and strategic behavior among the firms.

The Herfindahl-Hirschman Index (HHI) is a measure of market concentration, which indicates the degree to which a market is dominated by a small number of large firms. It is calculated by summing the squared market shares of all firms in the market.

Game theory is a mathematical framework that analyzes strategic decision-making in situations where multiple players interact and their actions affect each other's outcomes. It is used to understand and predict behavior in various fields, including economics, politics, and biology.

In a Cournot oligopoly, firms compete by setting quantities of output, assuming that other firms' quantities are fixed. Each firm chooses its output level to maximize its profit, taking into account the impact of its decision on the market price and the profits of other firms.

The Nash equilibrium is a set of strategies in a game where no player can improve their outcome by changing their strategy while the other players' strategies remain unchanged. It is a fundamental concept in game theory and is used to analyze strategic interactions in various economic and social contexts.

The kinked demand curve model is used to explain price rigidity in oligopolistic markets. It suggests that firms in an oligopoly may be reluctant to change their prices because they fear that other firms will respond in a way that will harm their profits. This leads to a kink in the demand curve, which makes it less responsive to changes in costs or market conditions.

In a Bertrand oligopoly, firms compete by setting prices, assuming that other firms' prices are fixed. Each firm chooses its price to maximize its profit, taking into account the impact of its decision on the market demand and the profits of other firms.

The concept of contestable markets suggests that even a monopolist may face competition if entry into the market is easy. This is because potential entrants can threaten to enter the market and drive down prices, which disciplines the monopolist and prevents it from exercising excessive market power.

Electricity distribution is an example of a natural monopoly because it exhibits economies of scale, meaning that the average cost of production decreases as the scale of production increases. This makes it more efficient for a single firm to provide electricity distribution services to an entire region, rather than having multiple firms compete in the same market.

Product differentiation refers to the existence of products that are different in terms of their physical characteristics, quality, or brand image. This allows firms to compete on factors other than price, such as product features, quality, and marketing.

In a monopolistically competitive market, firms produce differentiated products and compete on both price and non-price factors, such as product features, quality, and marketing. This allows firms to have some market power and charge prices above marginal cost, but they still face competition from other firms offering similar products.

A perfectly competitive market is characterized by many buyers and sellers, homogeneous products, perfect information, and the absence of barriers to entry and exit. These characteristics ensure that firms are price takers and that the market price is determined by the forces of supply and demand.

Economies of scale refer to the decreasing average cost of production as the scale of production increases. This can be due to factors such as specialization, division of labor, and technological advantages.