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
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vigilantly attentive
alert to the problems
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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
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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
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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
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alertedsimple
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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:
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
"The ministry advises the public, especially young people, to remain fully alert and highly vigilant."
From BBC ● Aug. 23, 2026
On Wednesday, the government of Honduras placed 80 percent of that Central American country on drought alert.
From Barron's ● Aug. 20, 2026
Scientists home in on unique mutations on the cancer cells that are likely to alert the immune system.
From The Wall Street Journal ● Aug. 19, 2026
In spite of this, when he thrust his hands into the new opening, some of the insects were alert enough to sting.
From "A Girl Named Disaster" by Nancy Farmer
This could include individually assessed exclusion zones around victim's homes or workplaces and alerts that trigger police responses when conditions are breached.
From BBC ● Aug. 25, 2026
Russian authorities could boost those alerts to men across the country, raising the number in stages.
From The Wall Street Journal ● Aug. 23, 2026
“LinkedIn’s low-key a snitch for that,” Istomin said about the alerts.
From The Wall Street Journal ● Aug. 19, 2026
Facewatch said alerts remain visible on staff devices for up to an hour, and that it logs all misidentifications.
From BBC ● Aug. 17, 2026
When I stumble out of my bedroom, still in my nightclothes, a whacking sound alerts me that Mama is on a cleaning tear.
From "Girl in the Blue Coat" by Monica Hesse
The other man carried on and was eventually able to get help from a passing motorist, who alerted authorities.
From Barron's ● Aug. 24, 2026
A garlicky smell once alerted him to the presence of arsenic in sugar, while the spill of a concentrated solution cut through clothing “like the blow of a scimitar.”
From The Wall Street Journal ● Aug. 24, 2026
The links remained on the Scottish Borders Council website until officials were alerted to the issue by the BBC earlier this month.
From BBC ● Aug. 22, 2026
Jade said her nan was alerted by the smell of burning from the living room on Thursday afternoon and fled to join neighbours in the street who were also raising the alarm.
From BBC ● Aug. 16, 2026
He alerted Alexander Bickel and Floyd Abrams, respected constitutional lawyers who had agreed to take the case.
From "Most Dangerous: Daniel Ellsberg and the Secret History of the Vietnam War" by Steve Sheinkin
Activists have been building maps alerting people where the cameras are.
From Salon ● Aug. 14, 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
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 it wasn’t a simple matter of alerting management.
From The Wall Street Journal ● May 21, 2026
I’d skip fourth-period math and send Mr. Meyers an email alerting him to the fact that I’d taken over as the room 82 alternate.
From "Liar, Liar" by Gary Paulsen
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.
