cornerstone
[ˈkɔ:nəˌstəʊn]
例句与用法：
She'll need luck to get out of a tightcornerlike that.
她要靠运气才能摆脱那样的困境。
By defeating their main competitor this firm hascorneredthe wheat market.
这家公司击败了主要的竞争对手而垄断了整个小麦市场。
He fell and hit his head on thecornerof a box.
他跌倒时，头碰到箱子的一角。