warn
Americanverb (used with object)
-
warns,
present (3rd person singular)
-
warned,
past participle, past
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warning
present participle
-
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)
-
warns,
present (3rd person singular)
-
warned,
past participle, past
-
warning
present participle
verb
-
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
Synonym Usage
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
Derived Forms
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warnernoun
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prewarnverb (used with object)
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rewarnverb (used with object)
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unwarnedadjective
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well-warnedadjective
Inflected Forms
Participles
Conjugated Forms
Present
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warnsimple
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warnssimple
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have warnedperfect
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has warnedperfect
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am warningprogressive
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are warningprogressive
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is warningprogressive
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have been warningperfect progressive
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has been warningperfect progressive
Past
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warnedsimple
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had warnedperfect
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was warningprogressive
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were warningprogressive
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had been warningperfect progressive
Future
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.
See Examples For:
Scientists warn the intensity and frequency of extreme weather events will increase as global warming accelerates because of fossil fuel emissions.
From Barron's ● Sep. 28, 2026
The Egyptians continued to warn Israel up until 48 hours before the attack, one of these officials said.
From The Wall Street Journal ● Sep. 27, 2026
Regulators warn that respected community or religious figures can sometimes lend legitimacy to financial opportunities without realizing they are doing so.
From Salon ● Sep. 26, 2026
Lawmakers and AI industry leaders have also called for guardrails on the nascent technology, which experts warn could soon surpass human understanding.
From Los Angeles Times ● Sep. 25, 2026
To warn Wolf to stay out of sight, he gave a low, urgent ‘uff’.
From "Wolf Brother" by Michelle Paver
In the track, Swift warns a woman about her partner, with whom the singer had a toxic relationship.
From Barron's ● Sep. 28, 2026
It also apparently has some weird all-knowing knowledge, because it warns its clueless mom about all the evil characters conspiring to abort the baby.
From Slate ● Sep. 26, 2026
He warns bringing snacks or specialist drinks may undermine the impression candidates will want to give - that they're "serious and focused on the interview".
From BBC ● Sep. 25, 2026
As a nearby sign warns, “Mother isn’t quite herself today — do not touch, she needs her space.”
From Los Angeles Times ● Sep. 25, 2026
The slight shake of her head warns me to stop.
From "A Step from Heaven" by An Na
The PFA and global players' union Fifpro have repeatedly warned about the impact of an increasingly congested calendar on player welfare.
From BBC ● Sep. 29, 2026
Anthropic reportedly warned of “existential risks to humanity” in its IPO prospectus.
From The Wall Street Journal ● Sep. 29, 2026
Parts of Germany's Rhine are now unnavigable for most shipping, an industry group warned Tuesday, after the river dropped to an all-time record low following months of little rainfall and hot weather.
From Barron's ● Sep. 29, 2026
Amodei himself has warned that AI could pose a risk to humanity if developed badly.
From Salon ● Sep. 29, 2026
“Now don’t expect anything fancy,” Eulie warned me.
From "The Seven Wonders of Sassafras Springs" by Betty G. Birney
MarketWatch: What are the warning signs that bond investors are getting worried?
From MarketWatch ● Sep. 29, 2026
In lieu of warning Europe to evacuate, they pray and make a plan to cover their asses.
From Los Angeles Times ● Sep. 29, 2026
The pursuing police driver did not follow the Passat along the wrong carriageway, turned off the blue warning lights and headed along the A66 on the right side of the road, the watchdog said.
From BBC ● Sep. 29, 2026
As the climatologist Jeffrey Shaman writes in the Times, El Niño offers governments a chance to prepare, whether by funding firefighters or creating warning systems for residents during heat waves.
From Slate ● Sep. 28, 2026
When she pointed out Parker, it was with a warning.
From "Legendary Frybread Drive-In" by Cynthia Leitich Smith
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.
