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

See Examples For:

lest

In Borneo's West Kalimantan province, at lest 15 of the animals have been rescued from flames and haze since July, some stuck in plantations after fires cut off access to their forest home.

From Barron's ● Sep. 11, 2026

These aren’t even movies that you’d bring to the water cooler, lest you want a conversation with a coworker to fall flat after 10 seconds.

From Salon ● Sep. 2, 2026

Teams are always circumspect about doing anything too exotic during the preseason, lest they give regular-season opponents something to study.

From Los Angeles Times ● Aug. 14, 2026

But lest anyone confuse him with a mortal, he followed up with a pair of goals to become the tournament’s all-time leading scorer.

From Slate ● Jun. 22, 2026

Electric typewriters were forbidden lest they be bugged by MI6.

From "Spies: The Secret Showdown Between America and Russia" by Marc Favreau