warn
Americanverb (used with object)
-
warns,
present (3rd person singular)
-
warned,
past participle, past
-
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
-
to urge or advise to be careful; caution.
to warn a careless driver.
-
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.
-
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
-
(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
-
(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
-
warnssimple
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have warnedperfect
-
has warnedperfect
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am warningprogressive
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are warningprogressive
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is warningprogressive
-
have been warningperfect progressive
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has been warningperfect progressive
Past
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warnedsimple
-
had warnedperfect
-
was warningprogressive
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were warningprogressive
-
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:
The yellow alerts warn of minor impacts on the health and social care sector, with increased use of healthcare services by vulnerable people - who face a greater risk to life.
From BBC ● Nov. 12, 2026
Experts warn the scandal could also weaken Nvidia's role as a key driver of the AI boom.
From Barron's ● Nov. 12, 2026
I would be remiss in my duties if I did not warn others in our situation not to follow in our footsteps.
From Slate ● Nov. 12, 2026
Customers were livid, complaining online that the company had taken too long to warn them of the breach.
From The Wall Street Journal ● Nov. 10, 2026
“I’ll be fine. Remember, Little Pumpkin, your mother’s spirit is watching over you. She’ll warn you of any danger.”
From "A Girl Named Disaster" by Nancy Farmer
"It might last until the beginning of Christmas, but it won't last the full holiday," he warns.
From BBC ● Nov. 14, 2026
And he warns of the dire consequences of failing to do so.
From The Wall Street Journal ● Nov. 13, 2026
The CBS meteorologist for New York, Tony Sadiku, warns there is a possibility of severe storms later in the evening, which could hamper search and recovery efforts.
From BBC ● Nov. 12, 2026
Ukraine's air force said the "air alert" app -- which typically warns of incoming Russian drone and missile attacks -- had been "subjected to hostile interference".
From Barron's ● Nov. 2, 2026
Pa warns him: “Don’t spoil things in the meantime by acting too hastily.”
From "Vincent and Theo: The Van Gogh Brothers" by Deborah Heiligman
Kay said doctors warned her she could have died if her friend had found her just half an hour later.
From BBC ● Nov. 14, 2026
Early Saturday, he sought to assure Americans it remains "safe to fly" but warned it would take time to resume normal service.
From Barron's ● Nov. 14, 2026
Since then, some units in high-risk areas have instituted turn-in and lock-away procedures, and stationed personnel have been warned to expect device confiscations.
From Los Angeles Times ● Nov. 14, 2026
To introduce an element of pressure, researchers warned half the participants that failing to follow the smiling instructions could cost them $2 from their $6 payment.
From Science Daily ● Nov. 14, 2026
“She might call you a name,” I warned myself.
From "Ida B" by Katherine Hannigan
The study, published November 4 in Science Advances, points to a potentially powerful new way to detect early warning signs of cognitive decline.
From Science Daily ● Nov. 14, 2026
The Navy also sent out a warning with “cyber threat hygiene recommendations,” advising that sailors limit social media activity and turn off location app access to phone cameras and location data on personal devices.
From Los Angeles Times ● Nov. 14, 2026
The Los Angeles County Sheriff’s Department had issued a warning about these pranks.
From The Wall Street Journal ● Nov. 14, 2026
She is now warning others about the risks.
From BBC ● Nov. 14, 2026
Less of an apology than a warning, something I hope will make them turn back rather than maneuver all their equipment to the fourth floor.
From "The Brightwood Code" by Monica Hesse
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Idioms from The American Heritage® Idioms Dictionary copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.
