linchpin

noun

linch·​pin ˈlinch-ˌpin 

variants or less commonly lynchpin

1

: a locking pin inserted crosswise (as through the end of an axle or shaft)

2

: one that serves to hold together parts or elements that exist or function as a unit

the linchpin in the defense's case

Did you know?

In his 1857 novel, Tom Brown’s School Days, Thomas Hughes describes the “cowardly” custom of “taking the linch-pins out of the farmers’ and bagmens’ gigs at the fairs.” The linchpin in question held the wheel on the carriage, and removing it made it likely that the wheel would come off as the vehicle moved. Such a pin was called a lynis in Old English; Middle English speakers added pin to form lynspin. By the early 20th century, English speakers were using linchpin for anything as critical to a complex situation as a linchpin is to a wagon, as when Winston Churchill, in 1930, wrote of Canada and the role it played in the relationship between Great Britain and the United States, that “no state, no country, no band of men can more truly be described as the linchpin of peace and world progress.”

Examples of linchpin in a Sentence

This witness is the linchpin of the defense's case.

Recent Examples on the Web

Kriemler was initially drawn to de Amaral’s work because of her penchant for horsehair, a linchpin material for Akris handbags and also sometimes incorporated into jackets. — Miles Socha, Footwear News, 24 Oct. 2026

Kansas, long an afterthought in federal elections, could be an unlikely linchpin to Senate control. — Teo Armus, Washington Post, 18 Oct. 2026

And something more substantial, even, than the ongoing oddity of just where Washington Square Park fits into the scheme of things as it’s gone from an evident linchpin of the project to an apparent afterthought. — Kansas City Star, 17 Oct. 2026

The 31-year-old has since emerged as a linchpin in the Brewers’ lineup, working series-changing at-bats against All-Star pitchers Yoshinobu Yamamoto and Blake Snell. — Ryan Canfield Outkick, FOXNews.com, 16 Oct. 2026

Word History

Etymology

Middle English lynspin, from lyns linchpin (from Old English lynis) + pin; akin to Middle High German luns linchpin

First Known Use

13th century, in the meaning defined at sense 1

Rhymes for linchpin

• akin
• auxin
• buckskin
• chagrin
• crankpin
• deerskin
• foreskin
• fuchsin
• herein
• kingpin
• pigskin
• pinyin

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Kids Definition

linchpin

noun

linch·​pin ˈlinch-ˌpin 

: a pin inserted crosswise through something (as the end of an axle or shaft) to keep things in place