alert

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

Synonyms of alert

• awake
• vigilant
• watchful
• aware

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

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.

Recent Examples on the Web

In central defence, Saliba and Gabriel edge out Marquinhos and Pacho, although Gabriel must be alert to cover the space left behind by Mendes’s lung-bursting runs forward. —Sarah Shephard, New York Times, 29 May 2026

Instead of focusing primarily on outcomes, professors and clinics should be alert to burnout appearing not only as low performance but also as perfectionism, emotional shutdown, avoidance or people-pleasing. —Sharon A. Kuhn, Forbes.com, 28 May 2026

The fire grew to about 250 acres, according to wildfire alert nonprofit Watch Duty. —Sally Krutzig, Idaho Statesman, 27 May 2026

Last week, Tedros classified the Ebola outbreak as a public health emergency of international concern – one level below a pandemic in the United Nations agency's alert system. —Youri Benadjaoud, ABC News, 26 May 2026

Word History

Etymology

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).

First Known Use

1618, in the meaning defined at sense 1a

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