1. 不定式的否定式的构成
通常是将否定词 not或 never置于不定式之前，即构成 not to do或 never to do的形式，注意 not和 never一定要放在不定式符号 to的前面，而不是其后面：
The doctor advised me not to smoke. 医生劝我不要抽烟。
It’s politically short-sighted not to do so. 不这样做在政治上是短视的。
He strongly advised me not to do so. 他使劲劝我别这样做。
Take care not to break it. 小心别把它打破了。
Be careful not to break anything. 当心别打破什么了。
She had sense enough not to say anything about it. 她有足够的头脑不提此事。
Father warned me never to drive after drinking. 父亲警告我不要酒后开车。
Visitors are requested not to touch the exhibits. 参观的人请勿触摸展品。
【注意】若不定式为完成式和被动式，否定词应置于整个结构之前：
She pretended not to have seen him. 她假装没看见他。
It is nice not to be dependent on others. 不依靠别人是好的。
You were silly not to have locked your car. 你没锁车太傻了。
2. so as to do sth和 in order to do sth的否定式
对于这两个结构的否定式，通常是将否定词置于不定式符号 to之前，而不是置于整个结构之前或其他位置：
Study hard so as not to fail the exam. 努力学习，以免考试不及格。
He came in quietly in order not to wake his wife. 他轻轻进来，以免把他妻子吵醒。
Go in quietly so as not to wake the baby. 进去时不要出声，以免把宝宝吵醒。
Take every precaution so as not to catch cold.采取一切预防措施以免感冒。
We keep the window shut in order not to let the flies in. 我们把窗子关着以免苍蝇进来。
They hid themselves in the cave in order not to be seen by the enemy. 他们躲在洞穴里以免被敌人发现。
Please reply at once in order not to lose this opportunity of a lower price. 请立即回复，以免失去这次低价的机会。
They must have worn gloves in order not to leave any fingerprints. 他们一定戴上了手套，以防留下指纹。
