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

When the tech industry executive met with his son’s guidance counselor, the school confirmed that it rarely withheld diplomas from chronically absent pupils, lest these students suffer later in life.

From The Wall Street Journal • Apr. 3, 2026

If losing your home and its contents — lest we forget about them — would cause you financial distress, don’t get rid of your home insurance.

From MarketWatch • Mar. 28, 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

I kept my chatting to a minimum for the rest of that day, lest I drove my aunt crazy with conversation until she marched me back to the orphan asylum.

From "The Detective's Assistant" by Kate Hannigan