warn怎么用？ｗａｒｎ后该跟哪些词，先看2008年呼和浩特乌兰察布中考试卷中有这样一道题：

　　There are some dangerous fishes in this river, and I’ve warned Jack ______ here.

　　A. not to swim B. to not swim

　　C. swim not to D. to swim not

　　答案是A。许多考生对这个答案疑惑不解，究其原因是考生对warn后该跟哪些词没有掌握。为此，本人特作如下归纳。

　　warn作动词，有“对(人)警告，提醒(某事)，告诫”之意，常见用法有：

　　1. warn+ n/pron。例如：

　　I won’t warn you again.

　　我不再警告你了。

　　2. warn + n/pron + to do。例如：

　　The teacher often warns us to study harder.

　　老师常常告诫我们要更加努力地学习。

　　Parents often warn their children not to play with fire.

　　家长常警告孩子别玩火。

　　3. warn + n/pron + of [about] + n。例如：

　　The morning paper warned of serious delays at the airport.

　　晨报提醒大家注意机场误点情况严重。

　　We warned them about the serious situation that they would have to face.

　　我们给他们谈了他们要面对的严峻形势。

　　4. warn + n/pron + against + doing…/n。例如：

　　I was warned against my neighbor.

　　别人警告我要提防我的邻居。

　　The policeman warned him against crossing the road at that place.

　　 警察提醒他不要在那个地方横穿马路。

　　5. 后接从句，that常省略。例如：

　　I warn you it’s going to be very cold.

　　我提醒你天气会变得很冷的。

　　He warned his students that they would have to work very hard to pass.

　　他告诫学生必须非常努力才能通过考试。

　　温馨提示：上述用法中有些视情况可相互换用。例如：

　　医生告诫那个病人不要抽烟。

　　The doctor warned the patient not to smoke.

　　= The doctor warned the patient against smoking.

　　他被警告说桥上有危险。

　　There was danger on the bridge. Someone warned him.

　　= Someone warned him of [about] the danger on the bridge.

　　= Someone warned him that there was danger on the bridge.

有关warn的几条重要搭配

1. warn sb against doing sth 告诫某人不要做某事。如：
The doctor warned the patient against smoking. 医生告诫病人不要抽烟。
The teacher warned the children against playing on the street. 老师告诫孩子们不要在街上玩。
2. warn sb against [about] sb (sth) 告诫某人提防某人(某事) 。如：
He warned us against pickpockets. 他叫我们提防扒手。
The police have warned shopkeepers about the forged banknotes. 警察已通知各店主要留意假钞。
3. warn sb of sth 警告(通知)某人会有某情况。如：
We warned him of the danger. 我们警告过他有危险。
The teacher warned us of the test. 老师通知我们要考试。
【注】warn 一般不能接双宾语。上面第一句不能说成：We warned him the danger.
4. warn sb that-clause 警告某人……。如：
I have warned him that it is not allowed. 我警告过他这是不允许的。
Police warned drivers that the roads were icy. 警方提醒司机路面已结了冰。
We warned her that it would happen. 我们警告过她会发生这种事。
I warn you that it is dangerous to swim here. 我警告你，在这里游泳是很危险的。
5. warn sb (not) to do sth 告诫某人(不)要做某事。如：
I warned him to be careful. 我告诫他要小心。
I warned him to stay away. 我告诫他别靠近。
He warned me not to go out with her. 他告诫过我不要同她一起出去。
The doctor warned him not to eat oily food after the operation. 医生告诫他手术后不要吃油腻食物。
比较：He warned me not to going out at night. / He warned me against going out at night. 他叫我不要晚上出去。