cornerstone
/ˈkɔːnəstəʊn/noun
1- a stone that forms the base of a corner of a building, joining two walls隅石; 墙角石。
1.1
- an important quality or feature on which a particular thing depends or is based基石; 基础; 支柱：
a national minimum wage remained the cornerstone of policy.
国家最低工资仍是政策的基础。