warn
C1Neutral (used across all registers)
Definition
Meaning
To inform someone in advance about a possible danger, problem, or unpleasant situation.
To advise someone strongly to do or not do something; to give official or formal advice about a rule or requirement.
Linguistics
Semantic Notes
Involves a speaker (warner), a recipient, a message about a potential threat, and often a recommended action. Can imply authority or concern. Does not guarantee the recipient will heed the advice.
Dialectal Variation
British vs American Usage
Differences
No significant differences in core usage. Minor variations in typical phrasing (e.g., 'warn against' vs. 'warn about') are stylistic, not regional.
Connotations
Identical in both varieties. Associated with authority figures, public safety, legal obligations, and interpersonal concern.
Frequency
Equally frequent and central in both BrE and AmE.
Vocabulary
Collocations
Grammar
Valency Patterns
warn somebodywarn somebody about/of somethingwarn somebody that-clausewarn somebody to-infinitivewarn somebody against something/doing somethingwarn of somethingVocabulary
Synonyms
Strong
Neutral
Weak
Vocabulary
Antonyms
Phrases
Idioms & Phrases
- “Warn someone off”
- “A word to the wise (is enough)”
- “Sound the alarm”
- “He who ignores history is doomed to repeat it.”
Usage
Context Usage
Business
Used for compliance notices, risk disclosures, and management advice (e.g., 'The auditor warned of potential liabilities.').
Academic
Used in discussions of historical causality, predictive models, or ethical responsibilities (e.g., 'The study warns against overgeneralising the data.').
Everyday
Common in safety advice, parental guidance, and friendly advice (e.g., 'I warned you the soup was hot!').
Technical
Used in system alerts, hazard communications, and legal disclaimers (e.g., 'The software warns the user before deleting files.').
Examples
By Part of Speech
verb
British English
- The Met Office has warned of severe gales tomorrow.
- I must warn you that parking here is at your own risk.
- She warned him against investing in such a risky venture.
American English
- The National Weather Service warned of severe thunderstorms.
- I was warned not to walk alone in that neighborhood.
- The label warns consumers about potential side effects.
adverb
British English
- No common adverbial form in use.
American English
- No common adverbial form in use.
adjective
British English
- No common adjectival form in use.
American English
- No common adjectival form in use.
Examples
By CEFR Level
- My mother warned me.
- The sign warns people.
- He warned us about the dog.
- The teacher warned the students about the difficult test.
- I tried to warn you that the film was scary!
- They warned us not to drink the tap water.
- Economists are warning of a possible recession next year.
- The article warns against the overuse of antibiotics.
- She was duly warned of the consequences, but she proceeded anyway.
- The judge warned the counsel against attempting to introduce inadmissible evidence.
- Historians have long warned that such policies could lead to social unrest.
- The device emits an audible tone to warn operators of an impending system overload.
Learning
Memory Aids
Mnemonic
Imagine a WARning siren (WARN) blaring to alert people of danger.
Conceptual Metaphor
KNOWLEDGE IS A SHIELD (Warning provides knowledge to protect against harm).
Watch out
Common Pitfalls
Translation Traps (for Russian speakers)
- Do not confuse with 'угрожать' (to threaten). 'Warn' is about giving information, not making a threat.
- The structure 'warn someone against doing something' is more common than direct translation of Russian 'от'.
- The verb can be used without a direct object in English (e.g., 'I warned about the ice'), which may feel incomplete to Russian speakers.
Common Mistakes
- Incorrect: *'I warned him the danger.' Correct: 'I warned him about/of the danger.'
- Incorrect: *'They warned to not go.' Correct: 'They warned us not to go.' or 'They warned against going.'
- Confusing 'warn' with 'threaten'.
Practice
Quiz
Which of the following sentences uses 'warn' INCORRECTLY?
FAQ
Frequently Asked Questions
They are largely interchangeable. 'Warn of' is often used for more immediate, specific dangers ('warn of an avalanche'), while 'warn about' can be broader, giving more background ('warn about the risks of smoking').
Yes, in patterns like 'warn of/about something' (e.g., 'The sirens warned of the tornado.') or 'warn against doing something' (e.g., 'My doctor warned against skipping meals.').
Essentially yes; it emphasizes the advance nature of the warning ('forewarned is forearmed'). It's more formal and less common in everyday speech.
No. The act of warning is separate from the reaction. A sentence like 'I warned him, but he didn't listen' is perfectly natural.