linchpin

1. N-COUNT If you refer to a person or thing as the linchpin of something, you mean that they are the most important person or thing involved in it. 关键性人物(或事物)[with supp, usu N 'of' n]

He's the linchpin of our team and crucial to my long-term plans. 他是我们团队的关键人物，对我的那些长远计划很重要。