V-ing形式可相当于名词在句中作主语、宾语以及表语，下面就此分别作些讲解。

　　一、作主语

　　V-ing形式作主语时，谓语动词用单数。如：

　　Collecting information is very important to businessmen.

　　Doing morning exercises is good for health.

　　V-ing形式作主语时与不定式的区别：

　　不定式作主语表示具体某一次的行为。

　　V-ing形式作主语表示抽象或泛指的动作。

　　实际运用中一般可互换，差异不大，但下列几种情况除外：

　　①当表语是V-ing形式时，主语也要用V-ing形式；当表语是不定式时，主语也要用不定式。如：

　　Seeing is believing. (To see is to believe.) 眼见为实。

　　②在It's no use /no good/ a waste of time doing sth.等句型中一般用V-ing形式，而不用不定式。如：

　　It is no good keeping this secret.此事不公开没有什么好处。

　　It is a waste of energy arguing with her.和她争论是浪费精力。

　　③在It is important/ necessary/ easy to do sth.，It is + adj. + for (of) sb. + to do sth.等句型中通常只能用不定式，而不使用V-ing形式。如：

　　It is important for you to learn English well.

　　It is very kind of you to help us.

　　二、作宾语

　　V-ing形式可用作动词的宾语。如：

　　He finished reading the book yesterday.

　　She suggested our going there to help the farmers.

　　在admit, advise, avoid, can't help, consider, delay, deny, endure, enjoy, escape, excuse, finish, leave off, mind等动词后面通常接动名词作宾语。

　　在hate, like, prefer等动词后面，如果表示一般倾向，则多用V-ing作宾语，如果指特定的或某次具体的行动，则多用不定式。如：

　　She prefers walking to cycling.她宁愿步行，也不愿骑自行车。

　　在动词attempt, begin, can't afford, continue, deserve, hate, intend, like, love, need等动词(词组)后既可接不定式作宾语，也可接V-ing形式作宾语，两者意义区别不大。如：

　　I intended coming/to come to your house last night but it rained.昨天晚上我打算去你家，但天下雨了。

　　I prefer making/to make an outline before I make a speech.我喜欢讲话前先拟个提纲。

　　但有些动词虽既可接不定式，也可接V-ing形式，但两者意思相差甚远。如：

　　The lights are still on. Who forgot to turn them off last night?(灯未关)

　　The room is dark. I forgot turning the lights off last night. (曾关过灯)

　　这类动词(词组)有：remember, regret, mean, try, can't help等。

　　动词need，require，want作"需要"解，deserve作"应得"解，其后接V-ing形式应用主动式，用不定式则使用被动式。如：

　　The window needs (requires, wants) cleaning (to be cleaned).

　　They deserved punishing (to be punished) for what they had done.

　　V-ing形式也可用作介词的宾语。如：

　　He apologized to the teacher for being late.

　　Her family are all proud of having such a splendid house.

　　但要注意用作介词to的宾语时，极易与不定式发生混淆。如：

　　Let's get down to repairing the machine.

　　[误] Let's get down to repair the machine.

　　此类结构还有：in addition to除……外，admit to承认，devote oneself to献身于，be equal to能胜任；等于，be familiar to为……所熟悉，give one's mind to专心于，keep to坚持，look up to尊敬，lead to导致，look forward to盼望，object to反对，pay attention to注意，point to指向，stick to坚持，be used to习惯于，turn to求助于。

　　三、作表语

　　V-ing形式可作表语。如：

　　English is quite interesting.

　　Her job is teaching English.

　　V-ing形式作表语可分两种情况：1. 相当于形容词； 2.相当于名词。前者应注意与过去分词区别。如：

　　This news is really exciting. We are all excited at the news.(V-ing形式表主动，过去分词表被动)

　　The boys were all shocked by the shocking accident.

　　The parents were greatly disappointed by their disappointing son.

　　后者易与进行时结构相混，可从以下两个方面予以区别：

　　A.看主语是否是V-ing的执行者(即V-ing的动作是否是句子主语的动作)。是，则为进行时;不是，则为V-ing形式。如：

　　1. He is cleaning the street.他正在打扫大街。

　　2. His job is cleaning the street.他的工作是打扫大街。

　　例1中的clean是主语he的动作，为进行时。例2中的clean显然不是his job的动作，为V-ing形式。

　　B.看V-ing形式能否与主语对换位置。能者为V-ing形式，不能者则为进行时。如：

　　3. The most difficult problem is building the bridge base.

　　4. They are building the bridge base.

　　例3可以调整为："Building the bridge base is the most difficult problem."，故为V-ing形式。例4则不能(Building the bridge base are they.不正确。)，故为进行时。

　　(文/王振祥；英语辅导报高中一年级版 03～04学年第41期； 版权归英语辅导报社所有，独家网络合作伙伴新浪教育，未经许可，不得以任何形式进行转载。)