(4)作宾语补足语,如:Tell the children not to play on the street. 如果句中的谓语动词为see, hear, watch, notice, have, make, let等,作宾语补足语的动词不定式须将to省去,如:I saw a little girl run across the street.
(5)动词不定式在句中作宾语,如带有宾语补足语时,须先用it作形式宾语,而将该动词不定式后置,如:I don’t think it right to do it that way.
(6)作定语:动词不定式作定语时,须位于被其修饰的名词或代词之后,如:Is this the best way to help him? 和定语用的动词不定式如果是不及物动词,不定式后面就要用必要的介词,如:He is the man to depend on. 如果被不定式修饰的名词为place, time, way,不定式后面的介词,习惯上可以省去,如:The old man is looking for a quiet place to live.
(7)作状语:动词不定式可以作下列的状语:①目的状语: Every morning he gets up very early to read English. 为了强调不定式表示目的的作用,可在不定式前加in order to或so as to(以便或为了),但应注意in order to位于句首或句中均可,而so as to不能位于句首,如:She reads China Daily every day in order to (so as to) improve her English. 将表示目的的不定式置于句首,也可强调目的的作用,如:To master a foreign language, one must work hard at it. ②结果状语:They lived to see the liberation of their home town.他们活到亲眼见到了他们家乡的解放。③too + 形容词或副词 + 动词不定式,表示“足能…”的结果,如:You are old enough to take care of yourself now.
3、复合结构不定式:由for + 名词(或代词宾格)+ 动词不定式即构成复合结构的动词不定式。其中for本身无意义。for后面的名词或代词是不定式的逻辑主语,这种不定式在句中可作主语、表语、宾语、定语或状语,如:It is very important for us to get everything ready for the harvest. 当作表语用的形容词表示不定式的逻辑主语的性质或特征时,就用介词of而不用for引出不定式的逻辑主语,这些形容词一般有good, nice, kind, wise, silly, stupid, foolish, right, wrong, careless, impolite等,如:It is very kind of you to help him every day.
4、疑问词 + 动词不定式:疑问代词和疑问副词后可加动词不定式构成不定式短语,在句中可作主语、表语或宾语,如:How to prevent them from swimming in this river is a problem.
5、动词不定式的否定式:动词不定式的否定式是由not + 动词不定式构成,如:It’s wrong of you not to attend the meeting.
6、动词不定式的时态形式所表示的时间关系:(1)一般式:动词不定式一般式所表示的动作是和谓语动词所表示的动作同时发生,但在多数情况下,是在谓语动词所表示的动作之后发生,如:We decided to plant more trees this spring.(其后),They often watch us play table tennis.(同时);(2)完成式:动词不定式完成式所表示的动作发生在谓语动词所表示的动作之前,如:I am sorryto have kept you waiting.(3)进行式:动词不定式进行式所表示的动作正在进行中,而且与谓语动词所表示的动作同时发生,如:She happened to be writing a letter in the room when I came in.
7、动词不定式的被动语态用法:如果动词不定式的逻辑主语为这个不定式所表示的动作的承受者时,不定式一般就用被动语态形式,如:What is to be done next hasn’t been decided yet.