形式主語

綜述

形式主語it 作為形式主語的it並無實際語義，只是為滿足語法上的需要，避免句子頭重腳輕，它代替的是句子的邏輯主語，概括起來會有如下情況：

不定式作邏輯主語

如：It is very kind of you to give me a hand in time.

It is my pleasure to address the meeting.

It was pretty hard for him to bring up the child on his own.

從句作邏輯主語

如：It is so happened that the tickets were sold out.

It is extremely obvious that she has been lying about her identity.

It suddenly occurred to me that the message must have been hidden

between the layers of the briefcase.

動名詞短語作邏輯主語

這類句子遠不如前面兩種出現率高，主要在（no good,waste,useless,no use,dangerous）等詞語的後面用

如：It is no use reasoning with him.

It is no good reading in dim light.

作形式主語的代詞只能用it ，不能用that，this等詞。例如:

1） It is easier to lose friends than to make friends. 交朋友難而失去朋友比較容易。

2） It is important for modern young people to master at least two foreign languages. 掌握至少兩門外語對於當代年輕人來說是很重要的。

以上兩句中的it是形式主語，真正的主語是後面的不定式短語。

3） It is considered no good reciting without understanding. 不理解的背誦被認為是沒有好處的。

4） It is no use crying over spilt milk. 覆水難收。

以上兩句中的it是形式主語，真正的主語是V-ing形式。

5） It is a fact that English is being accepted as an international language.英語作為一門國際語言正日益為人們所接受，這是不爭的事實。（NMET,95）

6） It depends on the weather whether we will go. 我們去不去得看天氣行事。（其中的whether 不能換成if，因為if不能引導主語從句。）

以上兩句中真正的主語是名詞性從句。

it 作形式主語，主要分為下列三種情況：不定式作主語、動名詞作主語 和 名詞從句作主語。具體分析如下：

不定式作真正主語

主要用於下列句型：

⒈It + is/was + adj./n. (形容詞或名詞） +to do sth.

A. 名詞作表語。主要有a pity,a pleasure,an idea等。例如：

In fact________is a hard job for the police to keep order in an important football match. （2001上海高考題）

A. this B. that

C. there D. it （答案為D)

再如：It is a great pleasure to do this. 這樣做多好啊。

It is a good idea to think this way. 這樣考慮問題是個好辦法。

除be外，其他動詞也有跟名詞的情況。例如：

It seems a pity to waste the food. 浪費這些食物真可惜。

It requires efforts to master a foreign language. 掌握一門外語需要種種努力。

B. 形容詞或形容詞短語作表語。分兩種情況：

1）下列形容詞：kind,good,nice,clever,wrong,right,foolish,wise,unwise,stupid,rude,careless,cruel,brave,naughty,polite,selfish等詞作表語時，不定式前常可加一個由of引起的短語，來說明不定式指的是誰的情況。形容詞表示不定式邏輯主語的特徵，即形容詞用來描述不定式行為者的性格、品行等。例如：

It was foolish of you to leave school.你中途退學，真是傻瓜。

It was brave of her to speak out in public. 她能當眾大聲講話，真勇敢。

這種of sb. to do sth. 句型，of 的賓語可以作句子的主語。上面兩個句子可以改寫為：

You were foolish to leave school.

She was brave to speak out in public.

2）其他形容詞作表語，常見的形容詞有：necessary,hard， important,difficult,easy,possible，common等。例如：

It is necessary to use a short-wave radio to pick up the programmes. 必須用短波收音機才能收到節目。

如果要說明不定式表示的動作是誰做的，可以在不定式前加for + 名詞或代詞+ to do sth.(for 后的賓語不能作句子的主語）。名詞或代詞作不定式的邏輯主語，即表示不定式所指動作的執行者。在此句型中，形容詞只對不定式行為者作某種描述，而不涉及其品行。例如：

It is not hard for one to do a bit of good. 對於一個人來說做點好事並不難。

It,s common for leaves to fall from the trees in the fall. 秋天樹葉從樹上落下是件常事。

需要注意的是：動詞不定式作主語，一般情況下用it作形式主語，而把動詞不定式（從句）放在後面。也可以直接用不定式作主語。例如：

It is wrong to tell lies. = To tell lies is wrong. 撒謊是不對的。

但在疑問句和感嘆句中，只能用it作形式主語。例如：

Isn't it a good idea to have a walk around? 出去兜一圈難道不是一個好主意嗎？

What a pleasure it is to work with you! 同你一起工作是多麼愉快啊！

⒊It + v. + to do sth.

動詞不定式作主語時除動詞be以外，動詞take,cost， need,require,make,sound,occur 等也可用it作形式主語，而把動詞不定式放在後面。例如：

It took us three years to complete the project. 我們花費三年時間才完成了這項工程。

It sounds reasonable to do it this way.聽起來這樣做有道理。

It needed hard work to finish the job. 要完成這項工作需要努力地工作。

It didn,t occur to me to ask him to help me. 我根本沒想到要找他幫忙。

動名詞作真正主語

用於這種形式的是一些特定的形容詞和名詞。例如：

It was nice meeting you. 見到你真高興! （分別時用）

它與不定式作真正主語的區別在於，動名詞說到的動作已經發生。例如：

It is nice to meet you. （剛剛見面時用)

it 作形式主語，動名詞作真正主語主要用於下列句型：

It's +n.（名詞或名詞短語）/adj.（形容詞）+ doing sth.

1）下列形容詞后常用動名詞作真正主語：nice,good,useless,hard,foolish,enjoyable,worthwhile等。例如：

It is nice talking to you. 跟你交談真是愉快。

It's foolish behaving like that. 這樣的表現是很愚蠢的。

It is useless doing that. 那樣做沒用。

2）下列名詞或名詞短語作表語時常用動名詞作真正主語：use,good,fun,a waste of,job,task等。例如：

It's a waste of time doing this. 這樣做是浪費時間的。

It's no good (use) doing that. 那樣做沒好處（沒用）。

It's an awful job doing this. 做這事真是一件可怕的差事。

It's fun doing this. 做這事真有趣。

It is not an easy task doing this work. 做這工作真非易事。

名詞從句作真正主語

用it 作形式主語的結構主要用於下列句型：

It +謂語+名詞從句（主語從句、表語從句、同位語從句）

⒈It is +名詞+從句：這樣的名詞有a fact,a surprise,an honor（非常榮幸），a pity,common knowledge（常識）等。例如：

It is common knowledge that the full moon brings fair weather. 皓月兆天晴，這是常識。

It is a surprise that you gave such an answer to the question. 你對這個問題作了這樣的回答，令人吃驚。

⒉It is +形容詞+從句: 這樣的形容詞有natural,true,strange,necessary,important,obvious（很明顯），certain,wonderful,funny,possible,likely,probable等。例如：

It is certain that free medical care will be given to most people in our city. 我們城市的多數人將享受免費醫療，這是一定的。

It is probable that he has known everything. 很可能他什麼都已經知道了。

⒊It +動詞+從句：這樣的動詞有seem,happen,appear,look,matter,make,strike,occur（突然想起）等。

It appeared that he had a taste for music. 看來他對音樂有一定的鑒賞力。

It made us very happy that she was saved.她能化險為夷令我們大家很高興。

⒋It + be + 分詞+從句：這樣的分詞有 said（據說）， reported（據報道），believed（人們相信），known（眾所周知），decided（已決定），proved（已證實），thought,expected,annouced,arranged,amusing,puzzling,striking等。例如：

It is said that Li Hao has been to Europe.據說李郝去過歐洲。

It was amusing that a rabbit ran out of the empty box on the desk.桌上的空盒子里竟然跑出來一隻兔子，太有趣了。

需要說明的是，大部分連接詞引導的主語從句都可以用 it充當形式主語。例如：

It remains unknown when they are going to get married. 他們何時結婚依然不明。

It says in the newspaper that the enemy has been defeated. 報紙上報導敵人被打敗了。

形式主語：

It +be+(the)+adj.+for sb.+to do sth.