warn

warn — verb

1. to give information to someone about a dangerous or unpleasant thing that might

1.動詞及物 / 不及物B1
釋義

to give information to someone about a dangerous or unpleasant thing that might happen, so they can be prepared or avoid it

例句

The tour guide warned the hikers about the sudden storms that appear in the afternoon.

warn + object + about + danger

Rohan's mechanic warned him that the brakes were nearly worn out and unsafe.

warn + object + that-clause

同義詞
  • alert

    Stronger sense of urgency; often used for immediate, time-critical dangers

  • caution

    More formal; implies advising careful behaviour rather than informing about danger

  • notify

    Neutral delivery of information without the element of danger or urgency

反義詞
  • reassure

    To remove someone's worry about a possible danger

文法句型

warn + object + of/about + danger

warn + object + that-clause

warn + object + to-infinitive

warn + against + gerund

warn + of + noun (intransitive)

用法筆記

Common patterns: 'warn + object + about' for general dangers, 'warn + object + of' is more formal and frequent in official notices. 'Warn + object + that-clause' is the only pattern that allows expressing a full situation. The intransitive 'warn of' does not name a specific person being warned.

常見錯誤

❌I warned him the storm.
✅I warned him about the storm.
💡'warn' requires a preposition before the danger, not a double-object structure.
❌The sign warns to drivers about the bridge.
✅The sign warns drivers about the bridge.
💡'warn' takes a direct object without 'to'.
❌She warned that he is late.
✅She warned that the bridge might collapse.
💡'warn + that-clause' must describe a future or possible danger, not a current fact.

2. to tell someone firmly that their actions are wrong or dangerous and that they m

2.動詞及物B2
釋義

to tell someone firmly that their actions are wrong or dangerous and that they must change them

例句

Bao's mother warned him about the trouble he would cause by skipping classes.

warn + object + about + consequences of behaviour

The shopkeeper warned the teenagers against stealing sweets from the shelf.

warn + object + against + gerund

同義詞
  • admonish

    More formal and official; often used in disciplinary contexts

  • rebuke

    Stronger disapproval; implies sharp criticism for something already done

  • caution

    Softer; suggests carefulness rather than strong disapproval

反義詞
  • encourage

    To give positive support for someone's behaviour

  • praise

    To express approval of someone's actions

文法句型

warn + object + about + behaviour

warn + object + against + noun/gerund

warn + object + not to-infinitive

用法筆記

Frequently used in school, parenting, and workplace contexts where someone in authority corrects behaviour. 'Warn + object + not to-infinitive' is the most common pattern. Distinguished from sense 1 by focusing on the person's conduct rather than an external danger.

常見錯誤

❌She warned him to not smoke.
✅She warned him not to smoke.
💡In standard English, 'not to' is preferred over 'to not' after 'warn'.
❌The teacher warned about cheating the exam.
✅The teacher warned the students about cheating on the exam.
💡'warn' needs a direct object (who is being warned) and the correct preposition ('on' before 'exam').