lest

American  

[lest] / lɛst /

conjunction

1. for fear that; so that (one) should not (used negatively to introduce a clause expressive of an action or occurrence requiring caution).

   He kept his notes by his side lest faulty memory lead him astray.

2. that (used after words expressing fear, danger, etc.).

   There was danger lest the plan become known.

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idioms

1. lest we forget. see lest we forget.

lest British  

/ lɛst /

conjunction

1. so as to prevent any possibility that

   he fled the country lest he be captured and imprisoned

2. (after verbs or phrases expressing fear, worry, anxiety, etc) for fear that; in case

   he was alarmed lest she should find out

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Etymology

Origin of lest

First recorded before 1000; Middle English leste, contraction of the lesse the, thi les the; late Old English the lǣste, earlier thȳ lǣs the, literally, “whereby less that” ( thȳ instrumental case of the demonstrative and relative pronoun, lǣs less, the conjunction)

Example Sentences

Consumers naturally looked for the cheapest flight — and airlines wanted to position themselves as having the lowest fare lest they literally fall off the screen as a consumer scrolled through options.

From MarketWatch • Apr. 10, 2026

The podcasters announced that they had won a “commitment to editorial independence,” lest anyone think OpenAI CEO Sam Altman might be angling to turn their show into propaganda.

From Slate • Apr. 7, 2026

He’s on track to complete that job, he said, and the President has every reason to let him, lest Iran quickly rebuild.

From The Wall Street Journal • Mar. 26, 2026

As her kids struggle to hold back their reactions, lest she swing back the other way, her husband just wants to go to Red Robin for his birthday scoop.

From Los Angeles Times • Feb. 1, 2026

I had to tie my straw bonnet firmly under my chin lest it blow away in the wind as we picked up speed.

From "The Detective's Assistant" by Kate Hannigan