动词不定式（to + 动词原形）在句中可作主语、宾语、定语、状语、宾补等成分。
要点讲解
- 作主语：To learn English well takes time. 学好英语需要时间。（常用 it 作形式主语：It takes time to learn English well.）
- 作宾语：want to do, hope to do, plan to do, decide to do, agree to do 等。
- 作宾补：ask sb. to do, tell sb. to do, want sb. to do 等。
- 作定语：后置修饰名词：I have a lot of homework to do. 我有许多作业要做。
- 作目的状语：He came to see me. 他来看我。
- 疑问词+不定式：I don't know what to do. 我不知道该怎么办。
- 不定式的否定：not to do：He told me not to be late. 他告诉我不要迟到。
经典例句
- It's important to keep healthy.
保持健康很重要。 - She wants to be a doctor.
她想当医生。 - We stopped to have a rest.
我们停下来休息。
易错提醒
- stop to do（停下来去做）与 stop doing（停止做）含义不同；remember/forget 后接 to do 与 doing 意思也不同。