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

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

Others note that payments involve all sorts of security and encryption issues, lest someone’s financial information become exposed on an AI platform.

From MarketWatch • Apr. 25, 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

At one point housewives were admonished not to shake their dust mops outdoors lest that contribute to smog.

From Los Angeles Times • Mar. 26, 2026

“Men who have been intimate all their lives,” he observed, “cross the street to avoid meeting, and turn their heads another way, lest they should be obliged to touch hats.”

From "Founding Brothers: The Revolutionary Generation" by Joseph J. Ellis