Translation guide
The English verb "warn" covers a range of situations from giving a serious caution about danger to giving a mild heads-up. Japanese uses different verbs and expressions depending on the severity, formality, and whether you are warning against an action or informing about a fact.
To caution someone strongly about a real danger, risk, or serious negative outcome.
The most direct equivalent for a formal or serious warning. Often used in official contexts, signs, or when there is a clear danger.
He warned about the danger.
The doctor warned of the dangers of smoking.
To warn or caution, often used in everyday situations. It can also mean 'to be careful' or 'to pay attention'. Softer than 警告する.
My mother warned me to watch out for cars.
The teacher warned us not to be late.
To admonish or warn, often with a moral or disciplinary tone. Used in formal or literary contexts.
He warned against laziness.
To tell someone not to do something because it is risky or will have bad consequences.
A common pattern meaning 'to tell someone not to do something'. The verb before ない is in plain negative form.
He warned me not to touch it.
The police warned people not to walk around late at night.
A more direct and casual way to say 'don't do ~'. Often used in informal speech.
He told me not to go. (He warned me not to go.)
To inform someone about something (often negative or inconvenient) before it happens, so they can prepare.
To give advance notice, often used for warnings about future events or changes.
The company warned of job cuts.
A casual phrase meaning 'to tell in advance' or 'to warn beforehand'. Often used among friends or in informal settings.
To issue a warning or alert, often used in official announcements or public service messages.
To tell someone that there will be negative consequences if they do or don't do something.
A common conditional warning pattern. 'If you don't do ~, ~ will happen.' The tone can be serious or light depending on context.
I'm warning you, if you don't hurry up, you'll be late.
I warn you, if you don't do your homework, no video games.
Literally 'I'll warn you (in advance)'. Used to issue a direct warning or threat.
I'm warning you. If you do it again, I won't forgive you.
警告する (keikoku suru) is stronger and more formal, often used for serious dangers or official warnings. 注意する (chūi suru) is more common in daily life and can simply mean 'to be careful' or 'to caution' without a strong sense of alarm.
A tsunami warning was issued.
My mother warned me to be careful on the stairs.
In casual conversation, using 警告する can sound overly dramatic or stiff. For everyday warnings, use 注意する or a pattern like 〜ないように言う.
I warned my friend, 'You'll be late.'
She warned me that the boss was in a bad mood.
Here 'warned' is more like 'gave a heads-up', so 教えてくれた (informed me) is natural.
Just to warn you, it's going to rain tomorrow.
The government warned about heatstroke.