alert
Americanadjective
noun
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alerts
plural
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an attitude of vigilance, readiness, or caution, as before an expected attack.
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a warning or alarm of an impending military attack, a storm, etc..
We'd just boarded the bus when the alert sounded.
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the period during which such a warning or alarm is in effect.
verb (used with object)
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alerts,
present (3rd person singular)
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alerted,
past participle, past
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alerting
present participle
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to warn (troops, ships, etc.) to prepare for action.
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to warn of an impending raid, attack, storm, etc..
The radio alerted coastal residents to prepare for the hurricane.
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to advise or warn; cause to be on guard.
to alert gardeners to the dangers of some pesticides.
idioms
adjective
-
vigilantly attentive
alert to the problems
-
brisk, nimble, or lively
noun
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an alarm or warning, esp a siren warning of an air raid
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the period during which such a warning remains in effect
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-
on guard against danger, attack, etc
-
watchful; ready
on the alert for any errors
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verb
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to warn or signal (troops, police, etc) to prepare for action
-
to warn of danger, an attack, etc
Usage
What does alert mean? An alert is a warning or alarm, especially an alarm about dangerous weather or a military attack, as in The National Weather Service has alerts for tornadoes, hurricanes, Nor’easters, and other severe weather occurrences. Alert is also an attitude of readiness or caution, as in Tina was on alert for news of her son’s acceptance into college. Alert describes being fully attentive or wide awake, as in Sabine needs to be awake for several hours before she is alert and ready to work. You can be alert to the people and objects surrounding you. When you are alert, you’re ready to act or react instead of being surprised. But you can also be alert to concepts, ideas, and trends, ready to react to a change in others’ thoughts or to a change in the market. To alert means to advise or to warn, as with an alert. For example, your teacher might alert you that your big project is due soon, while a police department might alert the public about a dangerous person on the streets. Example: Alert the security team of the incident and then head home.
Synonym Usage
Alert, vigilant, watchful imply a wide-awake attitude, as of someone keenly aware of their surroundings. Alert describes a ready and prompt attentiveness together with a quick intelligence: The tourist was alert and eager to see the sights. Vigilant suggests some immediate necessity for keen, active observation, and for continuing alertness: Knowing the danger, the scout was unceasingly vigilant. Watchful suggests carefulness and preparedness: A stakeout requires watchful waiting.
Other Word Forms
Derived Forms
Inflected Forms
Nouns
Participles
Conjugated Forms
Present
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alertsimple
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alertssimple
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have alertedperfect
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has alertedperfect
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am alertingprogressive
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are alertingprogressive
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is alertingprogressive
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have been alertingperfect progressive
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has been alertingperfect progressive
Past
-
alertedsimple
-
had alertedperfect
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was alertingprogressive
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were alertingprogressive
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had been alertingperfect progressive
Future
Etymology
Origin of alert
First recorded in 1590–1600; 1940–45 alert for def. 4; from Italian all'erta, equivalent to all ( a ) “to, on the” + erta “lookout, watchtower,” originally feminine of erto, past participle of ergere from Latin ērigere to erect
Explanation
Alert! Alert! Alert! Did I get your attention? When you are alert, you are awake and ready. When you issue an alert you give warning, alerting people to, or notifying them of, a concern. Alert is one of the rare words that can be used in the same form as a noun, verb, and adjective. In all parts of speech, alert implies preparedness. The word is derived from the French a l'erte which translates to "on the watch." When you hear the word, imagine an alarm going off. The alarm is the alert. When you hear it, you have been alerted and you are now alert.
Vocabulary lists containing alert
The Best Starting Words for Wordle
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Common Five-letter Words for Wordle, List 3
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List 2
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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:
French authorities issued an orange alert for thunderstorms in large parts of the country's south-west, which have already been hit by power outages and transport disruptions.
From BBC ● Aug. 25, 2026
A 16-year-old boy has been arrested under the Terrorism Act after a security alert in Omagh, County Tyrone.
From BBC ● Aug. 24, 2026
At the training, an air-raid alert interrupted the buzz among the future paratroopers.
From Barron's ● Aug. 20, 2026
“There was very little time between the air raid alert and the explosions,” Petrov said.
From The Wall Street Journal ● Aug. 20, 2026
I’m on high alert, trying to arrange the pieces of this puzzle together, but I can’t get them to fit.
From "Red Flags and Butterflies" by Sheryl Azzam
Russian authorities could boost those alerts to men across the country, raising the number in stages.
From The Wall Street Journal ● Aug. 23, 2026
Now’s the time to set those price alerts for your preferred route and dates on Google Flights.
From The Wall Street Journal ● Aug. 21, 2026
The site alerts users when someone has viewed their profile—which can either help or hurt your dating plans.
From The Wall Street Journal ● Aug. 19, 2026
The company added that suspending a store is a "precautionary measure" to prevent further alerts while staff undergo additional training.
From BBC ● Aug. 17, 2026
Late in the afternoon, his control room supervisor alerts him that the water truck they’ve been waiting for all day is at the gate.
From "Dry" by Neal Shusterman and Jarrod Shusterman
The local authority removed the links when alerted to the situation by the BBC, but did not respond to a request for comment.
From BBC ● Aug. 22, 2026
The FAA review found that an air-traffic controller alerted Marine One about the American Airlines jet, which was taking off for Pensacola, Fla., but didn’t notify the plane’s pilots of the helicopter.
From The Wall Street Journal ● Aug. 12, 2026
They were alerted to their evacuation just the day before by Italy's consulate in Jerusalem.
From Barron's ● Aug. 10, 2026
A moderator error caused a delay in the removal, TikTok said, but the company alerted law enforcement to the situation, closed several subsequent streams within 90 seconds, and banned the account.
From BBC ● Aug. 9, 2026
When he located the woman, and determined that indeed she had MDR, Bayona alerted Farmer.
From "Mountains Beyond Mountains" by Tracy Kidder and Michael French
Its products also recently started recognizing designated people and alerting the homeowner.
From The Wall Street Journal ● Aug. 21, 2026
Meta Platforms Inc. is alerting thousands of employees that they’re being laid off, part of a previously announced restructuring aimed at reducing costs while the company invests heavily in artificial intelligence.
From Los Angeles Times ● Jul. 6, 2026
The carriages’ union blamed the Central Park Conservancy for not alerting them to the potential health hazard for the horses.
From Salon ● Jun. 20, 2026
One pathway works quickly through the nervous system, rapidly alerting the brain that essential amino acids are lacking.
From Science Daily ● May 28, 2026
But alerting just those few houses wasn’t enough to tip the alarm.
From "The Tipping Point" by Malcolm Gladwell
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.
