alert

1 of 3

adjective

ə-ˈlərt 

1

a

: watchful and prompt to meet danger or emergency

an alert guard

trying to stay alert to possible problems

b

: quick to perceive and act

mentally alert

2

: active, brisk

elicited an alert response

alertly adverb

alertness noun

alert

2 of 3

noun

1

: a state of careful watching and readiness especially for danger or opportunity

on 24-hour alert

2

a

: an alarm or other signal of danger

traffic alerts

They sounded the alert.

b

: an urgent notice

… an alert to parents … about new immunization requirements.

—Ann Schrader

3

: the period during which an alert is in effect

alert

3 of 3

verb

alerted; alerting; alerts

transitive verb

1

: to call (someone) to a state of readiness : warn

alerted the school board of a possible teachers' strike

alert the authorities

2

: to make (someone) aware of something

alerted the public to the dangers of pesticides

Phrases

on the alert

: looking for or expecting something (such as danger or an opportunity)

Drivers need to be on the alert for icy conditions.

always on the alert for a good bargain

Synonyms

Adjective

• Argus-eyed
• attentive
• awake
• observant
• open-eyed
• tenty [Scottish]
• tentie
• vigilant
• watchful
• wide-awake

Noun

• admonishment
• admonition
• alarm
• alarum
• caution
• forewarning
• heads-up
• notice
• warning

Verb

• advise
• caution
• forewarn
• wake
• warn

Choose the Right Synonym for alert

watchful, vigilant, wide-awake, alert mean being on the lookout especially for danger or opportunity.

watchful is the least explicit term.

the watchful eye of the department supervisor

vigilant suggests intense, unremitting, wary watchfulness.

eternally vigilant in the safeguarding of democracy

wide-awake applies to watchfulness for opportunities and developments more often than dangers.

wide-awake companies latched onto the new technology

alert stresses readiness or promptness in meeting danger or in seizing opportunity.

alert traders anticipated the stock market's slide

intelligent, clever, alert, quick-witted mean mentally keen or quick.

intelligent stresses success in coping with new situations and solving problems.

an intelligent person could assemble it fast

clever implies native ability or aptness and sometimes suggests a lack of more substantial qualities.

clever with words

alert stresses quickness in perceiving and understanding.

alert to new technology

quick-witted implies promptness in finding answers in debate or in devising expedients in moments of danger or challenge.

no match for his quick-witted opponent

Examples of alert in a Sentence

Adjective

An alert guard stopped the robbers.

He was tired and had trouble staying alert while he was driving.

She wasn't mentally alert enough to answer the questions.

An alert watchdog guarded the door.

Noun

They sounded an alert when enemy planes were approaching the city.

Medical officials have put out an alert to hospitals to look out for the virus.

The government has issued a terrorism alert.

Verb

Several neighbors alerted the authorities when they noticed strangers acting suspiciously.

The governor alerted island residents that a hurricane was coming.

The teacher alerted the students that tests would be given the next day.

Recent Examples on the Web

Adjective

Here's a breakdown of the three-tiered alert system from the NWS and what each level entails: High wind warning: Take action! —Ca Weather Bot, Sacbee.com, 22 June 2025

Be alert to warning signs: Educate yourself about the signs and symptoms of heat exhaustion and heat stroke. —Nc Weather Bot, Charlotte Observer, 22 June 2025

Noun

According to Reuters, the base was placed on high alert, and the threat was linked to the possibility of an Iranian missile attack in response to the U.S. strikes on nuclear facilities on Saturday night. —Gabe Whisnant, MSNBC Newsweek, 23 June 2025

The Army has been at the third of four levels of alert at most places in the region, the official said. —Tom Vanden Brook, USA Today, 23 June 2025

Verb

This protection can also alert you to phishing emails and ransomware scams, keeping your personal information and digital assets safe. —Kurt Knutsson, FOXNews.com, 24 June 2025

For example, if a vehicle backs up straight toward an ATM instead of driving normally, AI could detect this and trigger responses like alerting employees, sounding alarms or shutting down machines. —Stuart MacKinnon, Forbes.com, 24 June 2025

Word History

Etymology

Adjective

borrowed from French alerte, going back to Middle French a l'herte "on guard, on the watch," borrowed from Italian all'erta, originally in the collocation stare all'erta "to be on the watch," literally, "to be on the height" (with erta "height, hill, steep ascent," noun derivative from feminine of erto, past participle of ergere "to raise, elevate," going back to Vulgar Latin *ērgere, by syncope from Latin ērigere) — more at erect entry 1

Note: The earliest citation for the word in the Oxford English Dictionary suggests direct borrowing from Italian, or at least recognition of an Italian source: "In this place the Prince [of Orange] finding his rutters [cavalry soldiers] alert, (as the Italians say) with aduise of his valiant brother, hee sent his Trumpets to D. d' Alua …." (Sir Roger Williams, The Actions of the Lowe Countries, London, 1618, p. 27).

Noun

noun derivative of alert entry 1 (or borrowed from French alerte, derivative of alerte, adjective)

Verb

verbal derivative of alert entry 1 or alert entry 2

First Known Use

Adjective

1618, in the meaning defined at sense 1a

Noun

1801, in the meaning defined at sense 1

Verb

circa 1868, in the meaning defined at sense 1

Phrases Containing alert

• Amber alert
• Blue alert
• hyper-alert
• on the alert
• red alert
• silver alert
• spoiler alert

Rhymes for alert

• assert
• avert
• dessert
• divert
• evert
• exert
• inert
• insert
• invert
• nightshirt
• overt
• revert

Kids Definition

alert

1 of 3 adjective

ə-ˈlərt 

1

a

: being watchful and ready to meet danger

b

: quick to understand and act

2

: active sense 3, brisk

alertly adverb

alertness noun

alert

2 of 3 noun

1

: a signal of danger

2

: the period during which an alert is in effect

alert

3 of 3 verb

: to call to a state of readiness : warn