What is a defining feature of the long run in microeconomics?

A defining feature of the long run in microeconomics is that all resources and all costs are variable. This means that firms have the flexibility to adjust their inputs, such as labor, capital, and raw materials, to achieve their desired output levels. In contrast to the short run, where some resources are fixed and cannot be changed (leading to constraints on production), the long run allows firms to optimize production by altering all factors of production.

In the context of this question, being able to vary all resources is crucial for firms to respond effectively to changes in market conditions, technology, or consumer preferences. This flexibility enables firms to expand capacity, innovate new products, or improve efficiency, ultimately influencing their competitiveness and profitability in the market.