A market condition in which sellers are so few that the actions of any one of them will materially affect price and have a measurable impact on competitors. 寡头卖主垄断一种由少数卖方控制的市场状况。因为卖主极少，以至卖主的任何行为都可能对价格产生实质影响，从而对其竞争对手产生相当大的冲击影响力
A market condition in which purchasers are so few that the actions of any one of them can materially affect price and the costs that competitors must pay. 寡头买主垄断一种由少量买方控制的市场状况，由于买主极少，以至于任一买主的行为都有可能极大地影响价格及竞买者所必须偿付的费用
