Lest

//lɛst// conj

conj ·Rare ·Advanced level

Definitions

Conjunction
  1. 1
    For fear that; that not; in order to prevent something from happening; in case. formal, literary

    "He won't go outside, lest he be eaten by those ravenous eagles."

  2. 2
    that (without the negative particle; introduces the reason for an emotion.) formal, literary

    "There was danger/alarm lest the plan become known."

Synonyms

All synonyms
beforecase

Example

More examples

"Beware lest you should miss the train."

Etymology

c. 1200, contracted from Middle English les te (“less that”), from Old English þȳ lǣs þe (“whereby less that”), from þȳ (instrumental case of demonstrative article þæt (“that”)) + lǣs (“less”) + þe (“that,” relative particle). The þȳ was dropped and the remaining two words contracted into leste.

Related phrases

in casejudge not lest ye be judgedlest we forget

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Data sourced from Wiktionary, WordNet, CMU, and other open linguistic databases. Updated March 2026.