alert
Americanadjective
noun
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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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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.
An Amber Alert has been issued for a 3-month-old boy believed to have been abducted from Northern California.
From Los Angeles Times • Jul. 1, 2026
The demand has already been unprecedented, Reuters reported, citing Trade Alert data.
From MarketWatch • Jun. 16, 2026
Abdirahman Mahamud, WHO director of Health Emergency Alert and Response Operations, said that the facility was a "local bilateral collaboration" between the US and Kenya and said dialogue was vital.
From Barron's • Jun. 9, 2026
“Even though it was originally made for the deaf and hard of hearing, it really has a huge following with college kids,” said BrieAnne McKenna, marketing director at Sonic Alert.
From The Wall Street Journal • Mar. 4, 2026
My ears warmed their way toward a Red Alert.
From "Darius the Great Is Not Okay" by Adib Khorram
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.
