No single buyer or seller is large enough or powerful enough to affect the price of the product. The second condition is that buyers and sellers deal with identical products. Therefore buyers do not prefer one seller's merchandise over another's because there is no disparity in quality, no brand names, and no need to advertise. The third condition is that each buyer and seller acts autonomously, there must be no collusion. If such a situation occurs, sellers would compete against one another for the consumer's dollar.
Buyers also compete against each other and against the seller to obtain the best price.
The fourth condition is that the buyers and sellers are knowledgeable about the items for sale. Because all products are exactly the same, customers would have little reason to remain loyal to one seller. If sellers were reasonably familiar with other sellers' prices, they would have to keep their own prices low to attract customers. It is up to the producer to keep prices competitive or new firms will enter the industry and take away some business. Since we live in a society were the five elements of pure competition are not available to us, then we are clearly operating in a state other than pure competition.