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

What seems to be happening is that businesses, flush with profits, are eating cost increases tied to higher oil prices lest they drive away customers.

From MarketWatch • Jun. 10, 2026

Some members of her party have pushed Sheinbaum to sever ties with Rocha Moya and other leaders suspected of links to organized crime, lest Morena be tainted by the allegations.

From Los Angeles Times • Jun. 3, 2026

There are many examples of match officials being placed in harmful situations but with individuals fearful of speaking out lest it exacerbates the situation or causes further alarm to friends, family and colleagues.

From BBC • May 15, 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

I dare not say where, lest this letter fall into unfriendly hands.

From "The Door in the Wall" by Marguerite de Angeli