作定语的不定式如果是不及物动词,或者不定式所修饰的名词或代词是不定式动作的地点、工具等,不定式后面须有相应的介词。例如：He is looking for a room to live in.
There is nothing to worry about.
Please give me a knife to cut with.
There / It is no use/ good/ not any use/ good/ useless doing sth.
admit,appreciate, avoid, consider, delay, enjoy, escape, excuse, feel like, finish, forgive, give up, imagine, include, keep, mention,mind,miss,practise, put off, resist, risk, suggest, can’t help, can’t stand(无法忍受)等。
I tried not to go there.(我设法不去那里。)
I tried doing it again.(我试着又干了一次。)]
mean to do 有意... mean doing意味着...
I mean to come early today.(我打算今天早些来。)
Missing the train means waiting for another hour.
allow, advise, forbid, permit
We don’t allow smoking here. We don’t allow students to smoke.
The window needs(requires, wants)cleaning(to be cleaned).
在短语devote to, look forward to, pay attention to, stick to, be used to, object to,thank you for, excuse me for 等后的动词也必须用动名词形式：I look forward to hearing from you soon.
Badly polluted, the water cannot be drunk.(原因)
Being written in haste, the composition is full of mistakes.
Having been deserted by his guide, he couldn’t find his way through the jungle.(为了强调已完成的动作)
Asked to stay, I couldn’t very well refuse.
这里 asked 可能意味着 having been asked, 也可能意味着when/since I was asked, 但用了 having been asked 就不会有歧义。