How to say "warn" in Japanese

• 言い聞かせるいいきかせるCommon
  ichidan verb, transitive verbCovers 'warn' in the mild sense of advising: patiently talking someone round so that they understand or behave, as a parent does with a child. It is really 'advise' or 'admonish', not a stern warning.
  私はいつも寛大かんだいであれと自分じぶんに言い聞いいきかせている。↗

  I always say to myself to be generous.
• 諭すさとすCommon
  godan verb, transitive verbMatches 'warn (against doing)': making someone recognize a fault or mistake and reasoning them out of it. Firm but reasoned admonition — picture a teacher or senior patiently talking someone round after they have done wrong.
  先生せんせいは生徒せいとたちに不注意ふちゅういを諭さとした。↗

  The teacher admonished his pupils for carelessness.

Both render the admonishing side of 'warn' — talking someone round rather than alerting them to danger: 「言い聞かせる」 for patiently advising or persuading someone, 「諭す」 for making them see a fault and reasoning them out of it.

Usage comparisons are AI-assisted and cross-checked by multiple models; for study reference only

• 言い聞かせるいいきかせるto tell
• 諭すさとすto make (someone) understand (a fault, mistake, etc.)
• 言ってのけるいってのけるto declare
• 言い聞かすいいきかすto tell
• 申し聞かせるもうしきかせるto tell
• 警鐘を鳴らすけいしょうをならすto sound a warning