Linchpin

/ˈlɪn(t)ʃpɪn/

Synonyms

  • cornerstone
  • essential part
  • foundational element
  • keystone
  • mainstay

Slang Meanings

The main person to rely on in a situation.
If you need to get this project done, talk to Jason; he's the linchpin.
A critical element that keeps things functioning.
Without the right funding, the entire operation will fall apart; the budget is the linchpin.