In a perfectly competitive market, what is the primary condition for long-term equilibrium to be reached?

In a perfectly competitive market, the primary condition for long-term equilibrium is that firms must earn zero economic profit. This means that the total revenue a firm earns is exactly equal to the total costs, including both explicit costs and opportunity costs. When firms are making positive profits, new firms are attracted to the market, increasing supply and driving prices down. Conversely, if firms are making losses, some will exit the market, decreasing supply and driving prices up. For example, if a bakery is making a good profit, new bakers will start opening shops, which will eventually lower profits for everyone until they stabilize at zero profit in the long run.