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

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

Speak out for them now, lest there be no one left to speak for you.

From The Wall Street Journal • Apr. 7, 2026

However, it’s important to remember how the regime came to be, lest we repeat the same errors.

From Los Angeles Times • Mar. 21, 2026

Among residents of the county, there were whispers that she’d locked herself away lest she go mad or that her mind was already unraveling under the strain.

From "Killers of the Flower Moon" by David Grann