什么情况下用动词不定式,即to加动词原形?

如果你想用动词在句子中充当主语、表语、宾语、状语和宾语补足语，也就是说充当除谓语之外的任何一种成份，你都可以用动词不定式。但要注意不定式与动名词的用法区别。 一动词不定式和动名词作主语的区别 (1) 不定式作主语经常表示具体动作，或者表示将要进行的动作。而动名词作主语经常表示抽象的一般性的动作。例如： It's no good for you to eat so much fat. (有具体的人for you) It's no good eating too much fat. (泛指) (2) 不定式的逻辑主语常用of, for 表示；动名词逻辑主语则常用物主代词、名词、代词表示。例如： It is stupid of you to write down everything the teacher says. (of you) It's no use your pretending that you didn't know the rules. (your) The doctor suggested them having their health check-up once a year. 二不定式与动名词做宾语的区别 (1) 动词后是接不定式还是动名词作宾语，主要是根据使用习惯。有些动词后一般只接不定式作宾语，而另一些则只用动名词作宾语。 (2) 介词后只能接动名词作宾语；还有少数结构后只用动名词作宾语。 (3) 在need, want, require 等后表示被动意义时，不定式要用被动语态，而动名词不需要。例如： My bike needs to be repaired. My bike needs repairing. （4) 英语中，有些动词动词后既可接不定式也可接动名词，意义区别不大，如：begin, continue, start, hate, like, love, need, require, want 等. 但在下列情况下, 一般要用不定式: would(should) 与 hate, like, love 连用时： I'd like to have a cup of coffee. *当begin, continue, start 等是进行式时 The students are starting to work on the difficult maths problem. *当begin, continue, start与know, understand 等连用时： I soon began to understand what was happening. （5）、部分动词后接不定式或动名词时, 意义差别较大。 forget, remember, regret 后接不定式, 表示现在或未来的动作, 接动名词表示动作已经发生。