warn
Americanverb (used with object)
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to give notice, advice, or intimation to (a person, group, etc.) of danger, impending evil, possible harm, or anything else unfavorable.
They warned him of a plot against him. She was warned that her life was in danger.
- Synonyms:
- forewarn
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to urge or advise to be careful; caution.
to warn a careless driver.
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to admonish or exhort, as to action or conduct.
She warned her employees to be on time.
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to notify, advise, or inform.
to warn a person of an intended visit.
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to give notice to (a person, group, etc.) to go, keep at a distance, etc. (often followed by away, off, etc.).
A sign warns trespassers off the grounds. A marker warned boats away from the dock.
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to give authoritative or formal notice to (someone); order; summon.
to warn a person to appear in court.
verb (used without object)
verb
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to notify or make (someone) aware of danger, harm, etc
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(tr; often takes a negative and an infinitive) to advise or admonish (someone) as to action, conduct, etc
I warn you not to do that again
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(takes a clause as object or an infinitive) to inform (someone) in advance
he warned them that he would arrive late
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(tr; usually foll by away, off, etc) to give notice to go away, be off, etc
he warned the trespassers off his ground
Related Words
Warn, caution, admonish imply attempting to prevent another from running into danger or getting into unpleasant or undesirable circumstances. To warn is to speak plainly and usually in strong terms: to warn him about danger and possible penalties. To caution is to advise about necessary precautions, to put one on one's guard about possibly harmful circumstances or conditions, thus emphasizing avoidance of undesirable consequences: to caution him against driving in such weather. Admonish suggests giving earnest, authoritative advice with only tacit references to danger or penalty: to admonish a person for neglecting his duties.
Other Word Forms
Etymology
Origin of warn
First recorded before 1000; Middle English warnen, Old English warnian; cognate with German warnen; Cf. ware 2
Explanation
When you warn someone, you advise them to be careful or tell them about a problem or danger. If you perform a dangerous stunt, you should probably warn your audience, "Don't try this at home." Many traffic signs are meant to warn drivers about hazards, like bridges that get slippery in the rain or bumps in the road. And the purpose of a dog's growl is to warn another dog (or human) that it's stressed or fearful. A warning is a helpful message, no matter what form it comes in, and to warn is to send this message. The Old English root is warnian, "give notice of impending danger."
Vocabulary lists containing warn
"The Secret Water"
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"The Black Ferris" by Ray Bradbury
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Tasting the Sky
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Example Sentences
Examples are provided to illustrate real-world usage of words in context. Any opinions expressed do not reflect the views of Dictionary.com.
Financial advisers warn ordinary investors about the significant risks and complexities of investing in pre-IPO companies.
From The Wall Street Journal • May 16, 2026
Methane is not considered toxic, but experts warn of the risks that emissions and air pollution pose to people in the surrounding area.
From Barron's • May 13, 2026
To the people that got a little too charred during his show, don’t say he didn’t warn you.
From Los Angeles Times • May 13, 2026
Researchers also warn that the chemicals could influence climate and atmospheric processes.
From Science Daily • May 13, 2026
I need to warn Max, but I can’t.
From "The Light in Hidden Places" by Sharon Cameron
Definitions and idiom definitions from Dictionary.com Unabridged, based on the Random House Unabridged Dictionary, © Random House, Inc. 2023
Idioms from The American Heritage® Idioms Dictionary copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.
