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• Achilles heel
  Achilles heel

  noun

  a portion, spot, area, or the like, that is especially or solely vulnerable.
• Achilles' heel
  Achilles' heel

  A point of vulnerability. (See Achilles.)

Achilles heel

American  

Or Achilles' heel

noun

1. a portion, spot, area, or the like, that is especially or solely vulnerable.

   His Achilles heel is his quick temper.

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Achilles heel British  

noun

1. a small but fatal weakness

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Achilles' heel Cultural  

1. A point of vulnerability. (See Achilles.)

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Achilles' heel Idioms  

1. A fatal weakness, a vulnerable area, as in This division, which is rarely profitable, is the company's Achilles' heel. The term alludes to the Greek legend about the heroic warrior Achilles whose mother tried to make him immortal by holding the infant by his heel and dipping him into the River Styx. Eventually he was killed by an arrow shot into his undipped heel. [c. 1800]

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Etymology

Origin of Achilles heel

First recorded in 1800–10

Example Sentences

"Banerjee's long electoral success rested on a delicate equilibrium between welfare and organisation. But the very organisation that sustained her for 15 years also became her Achilles' heel," says political scientist Bhanu Joshi.

From BBC • May 4, 2026

An inside look at the financials of both companies prior to funding rounds completed earlier this year shows their Achilles’ heel: the soaring costs needed to train new AI models.

From The Wall Street Journal • Apr. 6, 2026

As he notes, "this same virtue had become their experimental Achilles' heel: how do you "read" or "detect" a property that doesn't reside at any specific point?"

From Science Daily • Feb. 16, 2026

But Gauff's serve is her Achilles' heel and she double-faulted twice in her opening service game to gift the 24-year-old Baptiste the break back.

From Barron's • Jan. 23, 2026

Armed with 2,400 years' worth of extra mathematics, it is not hard for us to go back and find Zeno’s Achilles’ heel.

From "Zero: The Biography of a Dangerous Idea" by Charles Seife