n. the central building block at the top of an arch or vault
n. 拱顶石, 楔石, 重点
1. The keystone is the most important stone in an arch.
拱门中最重要的石头是拱心石。
2. In a successful team, communication is the keystone of collaboration.
在一个成功的团队中，沟通是合作的关键。
3. The keystone species plays a crucial role in maintaining the ecosystem.
拱心物种在维持生态系统中起着至关重要的作用。