the linchpin of somethingMAINthe person or thing in a group, system etc that is most important, because everything depends on them 〔团体、制度等的〕关键人物[事物]the linchpin of something• The modesty of the Arab woman is the linchpin of the whole political system.• My mother had always been the linchpin of our family.• Erme was the linchpin of the whole thing.• Apparently she accepted that she was the primary caretaker of her children and the linchpin of family life.
→ the linchpin of something at linchpin(1)