English definition of “warn”
/wɔːn/ verb [T]
OF DANGER › to tell someone that something bad may happen in the future, so that they can prevent it: [+ that] I warned you that it would be cold but you still wouldn't wear a coat. I've been warning him for months.
ADVISE › to advise someone not to do something that could cause danger or trouble: [+ to do sth] I warned you not to tell her.