keystone
n
1 (architecture 建) central stone at the top of an arch locking the others into position 拱顶石.
2 (usu sing 通常作单数) (fig 比喻) most important part of a plan, an argument, etc on which all the other parts depend (计划、 论据等的)基础, 主旨
Belief in a life after death is the keystone of her religious faith. 她的宗教信仰的基础是相信死後有来生. Cf 参看 corner-stone (corner1).
🗣️ 情景例句
and a good night's sleep.
睡一个好觉。
That's a good idea.
那是一个好主意。
As a result, the fish just eat and eat and grow and grow in the lovely warm water.