Microeconomics is commonly known as Price theory. To understand this, let's break down the basics of microeconomics and its relation to price theory.

Microeconomics:
- Microeconomics is a branch of economics that studies the behavior of individuals and firms in making decisions regarding the allocation of scarce resources and the interactions among these individuals and firms.
- It deals with the analysis of individual markets, demand and supply, consumer behavior, and the determination of prices and quantities of goods and services produced and consumed.

Price theory:
- Price theory is a fundamental part of microeconomics as it focuses on how the price and quantity of goods and services are determined in a market.
- It studies the factors that affect the pricing of goods and services, as well as the impact of prices on consumer behavior, production decisions, and market equilibrium.

Here are some key aspects of price theory in microeconomics:
1. Demand and Supply: Price theory analyzes how demand and supply interact to determine the price and quantity of goods and services in the market. Demand refers to the quantity of a good or service that consumers are willing and able to buy at different prices, while supply refers to the quantity of a good or service that producers are willing and able to sell at different prices.
2. Utility and Consumer Choice: In microeconomics, utility refers to the satisfaction or benefit that consumers derive from consuming a good or service. Price theory helps in understanding how consumers make choices based on the utility they derive from different goods and services while considering their budget constraints.
3. Production and Cost: Price theory also examines the production decisions of firms, including how they allocate resources to produce goods and services at the lowest possible cost. This involves analyzing the relationship between inputs (such as labor and capital) and outputs (the goods and services produced), as well as the costs associated with different levels of production.
4. Market Structures: Microeconomics also deals with the analysis of different market structures, such as perfect competition, monopoly, monopolistic competition, and oligopoly. Price theory helps in understanding how the behavior of firms, the level of competition, and the determination of prices and quantities vary across these different market structures.
5. Market Failure and Government Intervention: Price theory also plays a crucial role in identifying market failures, such as externalities, public goods, and imperfect information. These market failures may lead to inefficient allocation of resources, which may necessitate government intervention to correct the market inefficiencies.

In summary, microeconomics is also known as price theory because it focuses on the determination of prices and quantities of goods and services in the market, as well as the analysis of consumer behavior, production decisions, and market structures.