to make someone realize a possible danger or problem, especially one in the future

[ + obj + to infinitive ] We were warned not to eat the fish which might upset our stomachs. 我们被告诫不要吃那种鱼，因为可能会导致胃部轻微不适。

[ + obj + (that) ] Have you warned them (that) there will be an extra person for dinner? 你有没有提醒他们会多一个人吃饭？

I was warned against/off going to the east coast because it was so full of tourists. 有人告诫我不要去东海岸，因为那里游客爆满。

The boating area is marked with buoys to warn off swimmers. 划船区用浮标指示，警告游泳者不要进入。

There were signs warning of fog as soon as we got onto the motorway. 我们一上高速公路，就看到有“大雾”的警示牌。

This particular curry is extremely hot - be warned! 这种特别的咖哩食品极辣——小心食用！

Put that ball down now, Laura - I'm warning you (= I will punish you if you do not)! 放下那个球到这儿来，劳拉——我是在警告你！