非谓语动词在句中充当除谓语以外的句子成分的动词形式叫做非谓语动词
非谓语动词分为三种形式:不定式、动名词和分词(分词包括现在分词和过去分词)不定式一、不定式的作用1、 作主语 不定式作主语时,谓语用单数
往往用 it 作形式主语,把不定式放在谓语后面
如:It took us two hours to finish the job
It is impossible for us to get there on time
It is very kind of you to help us
注意:(1)其他系动词如 look, appear 等也可用于此句型
(2)当不定式作主语的句子中又有一个不定式作表语时,不能用 It is …to…的句型
试比较: It is to believe to see
(错) To see is to believe
(对)“百闻不如一见” (3)It is+ adj
of / for sb
to do sth
结构中,当不定式的逻辑主语和前面的形容词可以构成系表结构时,用 of, 否则用 for
2、 作宾语(1)动词+不定式
如:He managed to escape from the fire
I find it hard to get along with him
(it 作形式宾语)(2)动词+疑问词+to , “特殊疑问句+不定式”相当于名词,作宾语
如:I don’t know what to do next/ how to do it next
I can’t make up my mind which to buy
注意:不定式短语作宾语时,如果还带有宾语补足语,往往把不定式短语放在宾语补足语之后,用 it 作形式宾语
如:I find it necessary to learn a foreign language