Meaning & use
warn
Last updated
Meanings
verbtransitive or intransitive
To tell someone that something dangerous or unpleasant might happen, so they can be careful.
Grammar: Often followed by about, of, or a that-clause: warn her about the ice.
Patterns
- warn someone about something
- warn someone that
- warn of something
The lifeguard warned the swimmers about the strong current.
Scientists warn that sea levels will rise.
I warned him that the road would be icy.
verbtransitive
To advise or order someone not to do something, or to do it differently, to avoid trouble.
Grammar: Often followed by an infinitive: warn someone to stay away, warn someone not to go.
Patterns
- warn someone to do something
- warn someone not to do something
- warn someone against something
The teacher warned the class not to talk during the test.
My parents warned me to keep away from the river.
Police warned residents to stay indoors.
verbtransitive
To give someone official notice that they may be punished if they repeat bad behavior.
Grammar: Often used for rules or law: the officer warned him.
Patterns
- warn someone for something
The referee warned the player after the foul.
The officer warned the driver for speeding but did not fine him.
Staff were warned that any further lateness would be recorded.
Word forms
| third person singular | warns |
|---|---|
| past tense | warned |
| past participle | warned |
| -ing form | warning |
Common combinations
- warn of danger
- Signs warn of danger ahead.
- warn against
- Doctors warn against skipping meals.
- warn someone off
- The guard dog warned strangers off.
- repeatedly warn
- Experts have repeatedly warned that the dam is unsafe.
- warn in advance
- I will warn you in advance if the schedule changes.
- be warned
- Be warned that the trail gets steep.
Synonyms and how they differ
- alert
- Alert means to make someone aware of a situation quickly, while warn adds a note of coming danger.
- caution
- Caution is more formal and gentler, while warn can be stronger and direct.
- advise
- Advise just suggests what to do, while warn points to a specific risk.
- forewarn
- Forewarn stresses telling someone before the event, and is more formal than warn.
Opposites
Word family
Commonly confused: warn or worn?
warn vs worn
Worn is the past participle of wear and sounds like warn in many accents, but it means used or tired, not told of danger.
Practice
Yesterday the lifeguard ____ the swimmers to stay out of the water.
Choose one answer.
The time word yesterday needs the past tense warned. Warn and warns are present forms, and warning is an -ing form that cannot be the main verb here.
Make it your own
Write a sentence using “warn”, then check it and compare it with the examples above.