prevent，阻止、阻碍、阻挠。
prevent doing sth，阻止做某事。
prevent sb from doing sth，阻止某人做某事。
prevent通常会接所有格形容词+动名词或接受词+from+动名词。
当主词没有必要列出时，prevent可以直接接动名词，也可以接名词。
请结合经典例句，融会贯通：
You can't prevent my leaving.
你不能阻止我离开。
You can't prevent me from leaving.
你不能阻止我离开。
I want to prevent his getting sick.
我想防止他生病。
I want to prevent him from getting sick.
我想防止他生病。
This campaign is designed to prevent drowning.
这项运动旨在防止溺水。
He said this would prevent companies from creating new jobs...
他说这将使公司无法创造新的工作机会。
He is prevented by law from holding a licence.
法律不准他持有执照。
Some of the diseases of middle age may be prevented by improving nutrition.
中年时期的一些疾病可以通过改善营养的方式来预防。
A nasty incident was prevented by the timely arrival of the police.
警察的及时到来阻止了一次严重事故。
This can prevent air from flowing freely to the lungs.
这可以防止空气任意流入肺部。
The condition prevents the blood from circulating freely.
这种病阻碍了血液的循环畅通。
The drug prevents the virus from replicating itself.
这种药能防止病毒复制。
Further treatment will prevent cancer from developing.
进一步的治疗将阻止癌症恶化。
Put a lid on to prevent heat escaping.
盖上盖子，以免热气跑了。
It was too late to prevent the story from appearing in the national newspapers.
要阻止全国性报纸刊登这件事情已为时太晚。
We hope to prevent anything unpleasant from happening.
我们希望防止任何不愉快的事发生。
The rain prevented them from eating outdoors.
雨天使他们无法户外用餐。
The club's constitution prevented women from becoming full members.
这个俱乐部的章程不允许女性成为正式会员。
The police have been trying to prevent them carrying weapons.
警方一直都设法阻止他们携带武器。
Sure, I could have asked her, but something prevented me from doing so ．
当然,我本来可以问她的,但有件事阻止了我这么做。
We are working to prevent forest fires. 我们正在努力防止森林火灾。
These methods prevent pregnancy.
这些方法能防止怀孕。
They took active steps to prevent the spread of the disease.
他们采取积极措施，防止疾病蔓延。
We are taking steps to prevent pollution.
我们正在采取措施防止污染。
Snow has prevented communication with the outside world for three days.
大雪使得与外界的通信联系中断了三天。
Prisoners have been placed on lockdown to prevent further violence at the jail.
已对囚犯实行活动限制，以免狱中再出现暴力行为。
They were trying to prevent an even worse tragedy.
他们正在设法避免更大的悲剧发生。
A back injury prevented active participation in any sports for a while.
背伤曾一度妨碍积极参加任何体育运动。
Dressings are changed four hourly to help prevent infection.
每四小时更换一次敷料，以防感染。
Regular exercise helps prevent weight gain.
经常锻炼有助于防止体重增加。
Early identification of a disease can prevent death and illness.
病症的及早诊断可避免死亡与病痛。
These measures are aimed at preventing violent crime.
这些措施旨在防止暴力犯罪。
prevent sth/sb from doing sth
from可用可不用。使用from，则句型为主谓宾+介词短语作状语（现代语法称这个介词短语为动词的补足语）。
不用from，则句型为主谓宾结构，动名词复合结构作宾语。动名词的逻辑主语为代词时，正式语体用所有格表示，非正式语体用宾格表示。
Nothing would prevent him from speaking out against injustice.
什么都不能阻止他鸣不平。
Nothing would prevent him/his speaking out against injustice.
什么也阻挡不了他为不平之事鸣冤叫屈。