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

“O, swear not by the moon, th’ inconstant moon / That monthly changes in her circle orb / Lest that thy love prove likewise variable,” Juliet warned Romeo.

From Los Angeles Times • Jun. 3, 2026

Lest we forget that Bernie Madoff infamously used his social and country-club networks to recruit investors, running one of the largest “affinity frauds” in history.

From MarketWatch • May 27, 2026

Lest you believe it’s about falling in love, she adds later on: “If you think I’m talkin’ ’bout romance / You’re not listening.”

From The Wall Street Journal • Sep. 30, 2025

Watching from the Mall, Grace Gothard, from Mitcham, made her Union Jack dress draped with the Ghanian flag while Satvinder Cubb, from Chingford made a frock made from two "Lest we forget" scarves.

From BBC • May 5, 2025

Lest you think this journal has taken an unexpectedly dark turn, I should hasten to explain that he’s fine.

From "From Twinkle, with Love" by Sandhya Menon