Monopoly
A monopoly (from the Greek monos, one + polein, to sell) is when a product or service can only be bought from one supplier for a specific market.  If other firms serve the market, they may be too small compared to the largest, thus allowing the large firm to have a lot of market power. A monopoly usually happens when there is no economic competition to produce the product or service and there is no available substitutes to the product or service.