linchpin

Từ điển Oxford Advanced Learner 8th

linch·pin [linchpin linchpins] (also lynch·pin)BrE [ˈlɪntʃpɪn] NAmE [ˈlɪntʃpɪn] noun
a person or thing that is the most important part of an organization, a plan, etc, because everything else depends on them or it
•Nurses are the linchpin of the health service.
See also: ↑lynchpin

Word Origin:
late Middle English: from Old English lynis (in the sense ‘linchpin’) + ↑pin.

• Từ đồng nghĩa / Synonyms:
  lynchpin, anchor, mainstay, keystone, backbone