An important difference between the situation faced by a profit-maximizing competitive price-searcher firm in the short run and the situation faced by that same firm in the long run is that in the short run,
price may exceed marginal revenue, but in the long run, price will equal marginal revenue.
price may exceed marginal cost, but in the long run, price will equal marginal cost.
price may exceed average total cost, but in the long run, price will equal average total cost.
there are many firms in the market, but in the long run, there are only a few firms in the market.