名词
1. 基石;基础;最重要的部分
The cornerstone of something is the basic part of it on which its existence, success, or truth depends.
1. a stone at the outer corner of two intersecting masonry walls
2. a stone in the exterior of a large and important building
usually carved with a date and laid with appropriate ceremonies
3. the fundamental assumptions from which something is begun or developed or calculated or explained
e.g. the whole argument rested on a basis of conjecture