warn的用法及词组（warn相关短语）
1. warn SB (not) to do 警告、劝诫、劝说某人（不）要做某事
初高中学习是孩子处于青春期的阶段，也是孩子学习当中最关键的六年，因为它涉及到了中考与高考，左养中学教育赖颂强再讲孩子的学习方法和考试心里调节的直播课里，系统的讲解到如何帮孩子提升学习效率，提升考试时候的心理素质，从而提升学习成绩。
这个用法可以转化为被动语态：SB be warned (not) to do ,例如：
The doctor warned the patient not to eat oily food after the operation.=
The patient was warned not to eat oily food after the operation by the doctor.
医生警告过病人在手术后不要吃油腻食物。
I warned you not to buy that old car.
我劝过你不要买那辆旧汽车。
They wre warned not to climb the mountain in such bad weather.
有人劝诫他们不要在这么坏的天气去登那座山。
He warned me not to be late.
他提醒我不要迟到。
《牛津高阶英汉双解词典》
‘I warned you not to phone me,’ he said evenly.
“我告诫过你不要给我打电话。”他平静地说。
Police are warning the public to be on the alert for suspicious packages.
警方警告公众要警惕可疑包裹。
Mrs. Blount warned me not to interfere.
布朗特夫人警告我不要插手。
The police warned them not to go out at night.
警察告诫他们夜间不要出门。
He warned Billy to keep away from his daughter.
他警告比利离他女儿远点。
特别提示：warn sb about/against sb/sth提醒注意（可能发生的事）；使警惕
He warned the tourists against pickpockets.
他提醒游客要提防小偷。
He warned us against pickpockets.
他提醒我们要提防小偷。
The guidebook warns against walking alone at night.
这本指南告诫夜间不要单独行走。
2.warn of 警告……关于（危险等）；预告说……；通知说
Police have warned of possible delays.
警方已经通知可能会廷期。
Please give us advance warning of any changes.
如有变动，请事先通知我们。
It seems only right to warn you of the risk.
似乎应该警告你有风险。
The motoring organization is warning of thick mist and blowing snow on high ground.
汽车协会预告说在高地有大雾和风雪。
The government has warned of stormy waters ahead.
政府已告诫说，以后的局势将很严峻。
3. warn sb off (sth) （尤指以威胁的方式）叫…离开，告诫…不要靠近；
The farmer warned us off his land when we tried to camp there.
我们想在那里露营时，农场主警告我们不得靠近他的土地。
warn sb off doing劝…不要做；建议…停止做
We were warned off buying the house.
有人劝我们不要购买这所房子。
