object lesson

American  

noun

1. a practical or concrete illustration of a principle.

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object lesson British  

noun

1. a convincing demonstration of some principle or ideal

2. (esp formerly) a lesson in which a material object forms the basis of the teaching and is available to be inspected

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Etymology

Origin of object lesson

First recorded in 1825–35

Example Sentences

Industry insiders have told the BBC that Fishwick is now regarded as an object lesson in how not to run an installation project.

From BBC • Oct. 30, 2025

Put it all together, and the Boeing story looks like an object lesson in what happens when management takes its eye off the ball — or more precisely, puts it eye on the wrong ball.

From Los Angeles Times • Sep. 10, 2024

South Carolina State Conference of the NAACP, is an object lesson in the conflict between two competing theories of how we should think about racism in America today.

From Seattle Times • May 28, 2024

The fatal shooting of Nahel Merzouk in France on June 27 offers an object lesson.

From Slate • Jul. 20, 2023

The incredible effort of moving the boy to Boston, then watching him die, later struck me as an object lesson in the difficulty of Farmer’s mission, perhaps in its ultimate futility.

From "Mountains Beyond Mountains" by Tracy Kidder and Michael French