非谓语动词包括不定式、动名词和分词。否定形式在前面加not.

　　（一）不定式：to +动词原形

　　简单句中如果已经有一个动词做谓语，那么再有一个动词就要在这个动词前加to做不定式。不定式在句子中可以作主语、宾语、表语、宾语补足语、定语、状语等。

　　To see is to believe.（眼见为实）

　　有时用it做形式主语，真正的主语放在句子最后。

　　It only took us a year to finish the work.

　　Once you get into the habit of smoking， you’ll find it extremely difficult to get out of it.（get into the habit 养成……习惯）

　　She likes to play basketball this afternoon.

　　The important thing is to save people.

　　Not to grasp firmly is not to grasp at all.（不定式的否定放在to的前面）

　　She was the first person to think of the idea. （think of 想起）

　　He is always the first to come and last to leave the office.

　　I have nothing to say on the problem.

　　They warned him not to let out the secret.（let out 泄露）

　　We are all happy to hear of the good news.

　　Let’s hurry so as not to be late for the meeting. （so as to do sth. 以便为了做某事）

　　如果not不是放在to的前面，那么它不是否定不定式而是否定整个句子。

　　They didn’t warn him to let out the secret.

　　They warn him not to let out the secret.

　　（一）不定式：to +动词原形

　　不定式在let， have， make （让， 使）， see， look at， notice， hear， listen to， feel 等后面作宾语补足语时to 应省略，在被动语态中to应保留。

　　The coach has the team practice hard every night in the past two years.

　　I saw a man come into the classroom and talk with the teacher.

　　Don’t forget to have him come tonight.

　　We felt the house shake.

　　The house was felt to shake.

　　Someone was heard to come up the stairs.

　　在help 后， 不定式可以带to 也可以不带to.

　　Help me （to） get him to bed.

　　He help her lift the box.

　　He helped her to mount the bike.

　　She was helped to lift the box.

　　当不定式和其修饰的词有动宾关系时，动词如果是不及物动词，后面就要有必要加介词。

　　There is nothing to worry about.

　　Is this something to be ashamed of ？

　　I need a pen to write with.

　　Give me some paper to write on.

　　Let’s find a room to put the things in.

　　2、不定式的逻辑主语

　　不定式前面可以加for 或of引导的短语作逻辑主语，说明不定式表示的动作是谁做的，或不定式指的是谁的情况。

　　It is a great honor for us to be present at this party.

　　It will be a mistake for us not to help them.

　　It is hard for one to do a bit of good.

　　在某些形容词如kind， good， nice， wise， unwise， clever， silly， wrong， right， foolish， stupid， careless， considerate， rude， naughty， impolite等作表语时，用of引导短语。

　　It’s kind of you to let me use your dictionary.

　　It’s unwise of them to turn down the proposal.（turn down 拒绝）

　　It’s very nice of you to attend our party tonight.

　　3、不定式的完成式、进行式、被动式

　　当不定式所表示的动作在谓语所表示的动作之前发生时，不定式要用完成式： to have +过去分词；当不定式的动作与谓语所表示的动作同时发生时，不定式要用进行时：to be+现在分词；当不定式的逻辑主语是不定式所表示的动作的承受者时，不定式要用被动式：to be+过去分词。完成式意味着不定式的动作发生在谓语动作之前，如果是进行时意味着不定式的动作和谓语动作同时发生，当不定式的逻辑主语是不定式所表示的动作的承受者时，不定式要用被动式。

　　I’m sorry to have given you so much trouble.

　　I meant to have told you about it， but I forgot to do so.

　　They seemed to be satisfied with the result.

　　This is the day not to be forgotten.

　　He wanted the letter to be typed at once.

　　They seem to be getting along quite well.

　　He pretended to be sleeping when his mother came in.

　　在有些结构中，不定式的逻辑主语虽然是不定式所表示的动作的承受者，不定式仍用主动形式

　　We have a lot of work to do.

　　Give me something to eat.

　　They found the book hard to understand.

　　He has no one to take care of. （take care 照顾、照料）

　　没有什么人需要他照顾。

　　He has no one to take care of him.没有谁照顾他。

　　一个简单句同时出现两个动词时，在后面的动词前加to.使意动词和感观动词主动语态前不加to.不定式的完成式、进行式、被动式的概念。

　　不定式在句子中可以作主语、宾语、表语、定语、状语（主要是目的状语）、宾语补足语。