Synonyms

warn

American

[wawrn] / wɔrn /

verb (used with object)

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.
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.
to give authoritative or formal notice to (someone); order; summon.

to warn a person to appear in court.

verb (used without object)

to give a warning; caution.

to warn of further disasters.

warn British

/ wɔːn /

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
(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

"Collins English Dictionary — Complete & Unabridged" 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

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

Inflected Forms

Participles

Conjugated Forms

Present

Past

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."

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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:

warn warns warned warning

Analysts warn that these savings are by no means guaranteed.

From BBC ● Aug. 17, 2026

Sometimes authorities warn hours before a likely attack.

From Barron's ● Aug. 16, 2026

Signs placed along a service road warn of the presence of the federally threatened California red-legged frog at Diablo.

From Los Angeles Times ● Aug. 16, 2026

Western military officials also warn that Russia is systematically using its own drones to probe Europe’s air defenses.

From The Wall Street Journal ● Aug. 14, 2026

“But what I was going to say is that the vet took a gamble with Klawde today, and he lost. You did warn him.”

From "Klawde: Evil Alien Warlord Cat" by Johnny Marciano and Emily Chenoweth

And, he warns, even if rain returns, some of the agricultural damage may already have been done.

From BBC ● Aug. 15, 2026

At the same time, Yoshida warns against thinking too literally.

From The Wall Street Journal ● Aug. 12, 2026

New research warns that prolonged periods of unusually warm ocean temperatures can also threaten human physical and mental health.

From Science Daily ● Aug. 11, 2026

The CDC warns that electric fans can actually raise your body temperature in extreme heat.

From Los Angeles Times ● Aug. 11, 2026

“It’s what the doctor warns us of. There is no medicine that can cure him.”

From "Homeless Bird" by Gloria Whelan

“The risk-taking can be happening in secret, and that gets into violating trust and financial infidelity,” Taylor warned.

From MarketWatch ● Aug. 18, 2026

Goldman Sachs warned last week that diesel faces a greater risk of persistent scarcity than crude as winter approaches, noting the market was already tight before the Iran war began.

From The Wall Street Journal ● Aug. 18, 2026

He described it as a "target contract" and warned it would be "very difficult" to sustain workforce numbers if the yard did not secure the work.

From BBC ● Aug. 18, 2026

With the two at loggerheads, analysts warned that the crisis could drag on, keeping oil prices elevated and putting pressure on inflation.

From Barron's ● Aug. 17, 2026

If Old Timothy had served as master of hounds for the day, that meant it was Old Timothy who had blown the horn that warned her and the children that Lord Fredrick was coming.

From "The Unseen Guest" by Maryrose Wood

The children's commissioner for England is warning that kids in the UK are "becoming intoxicated by extremism" on social media, the Times reports.

From BBC ● Aug. 18, 2026

There, an extreme heat warning has been issued, with Las Vegas expecting highs up to 108 degrees, the Phoenix area up to 112 degrees and Death Valley potentially 118 degrees.

From Los Angeles Times ● Aug. 17, 2026

Tapper pressed Cassidy on whether Kennedy’s history should have been warning enough.

From Salon ● Aug. 16, 2026

The police in Dendermonde, a city of around 50,000 in the Flanders region, 18 miles northwest of Brussels, are warning potential scourers to stay away.

From The Wall Street Journal ● Aug. 16, 2026

That was when she’d run to the cave and screamed a warning to Torak -and got nothing back but echoes.

From "Wolf Brother" by Michelle Paver

Definitions and idiom definitions from Dictionary.com Unabridged, based on the Random House Unabridged Dictionary, © Random House, Inc. 2023