Free exit refers to the ability of firms to leave a market without facing significant barriers or costs. This concept is crucial in both perfect competition and monopolistic competition, as it allows firms to respond to unfavorable market conditions by ceasing operations, which contributes to long-term market efficiency and ensures that resources are allocated to their most productive uses. Free exit helps maintain competitive pressure in the market, as firms that cannot cover their costs will naturally exit, allowing only the most efficient firms to survive.