it可用作人稱代詞、指示代詞、先行詞及引導詞等。
1. 人稱代詞it，是第三人稱單數中性，代表前文已提到過的一件事物。如：
1）That vase is valuable. It's more than 200 years old. 那個花瓶很珍貴，它有200多年的歷史。
2）I love swimming. It keeps me fit. 我喜歡游泳，它能使我保持健康。
當說話者不清楚或無必要知道說話對象的性別時，也可用it來表示。 如：
3）It's a lovely baby. Is it a boy or a girl? 寶寶真可愛，是男孩還是女孩？
it可用來指代團體。如：
4）The committee has met and it has rejected the proposal. 委員會已開過會，拒絕了這項建議。
it用以代替指示代詞this, that.如：
5）--- What's this? --- It's a pen. —這是什麼？ —是一支鋼筆。
6）--- Whose book is that? --- It's Mike's. —那是誰的書？ —是邁克的。
2. 指示代詞it，常用以指人。如：
7）Go and see who it is. 去看看是誰。
8）--- Who is making such a noise? —是誰發出這樣的吵鬧聲？
--- It must be the children. —一定是孩子們。
3.虛義it無指代性，常用作沒有具體意義的主語，出現於表示天氣、氣候、溫度、時間、地點、距離等意義的句子中。如：
9）It is half past three now. 現在是三點半鐘。
10）It is six miles to the nearest hospital from here. 這裡離最近的醫院也有六英里。
11）It was very cold; it snowed and grew dark.
天氣很冷；天下著雪，漸漸地變黑了。
it也常用來表示一般的籠統的情況。如：
12）It's awful—I've got so much work I don't know where to start. 糟透了——我有這麼多工作要做我不知從何開始。
13）How is it going with you? 你近況如何？
14）Take it easy. 不要緊張。
it也常用於下列結構：
15）It looks as if the college is very small. 看起來這個學院很小。
16）It seems as though our plan will be perfect. 似乎我們的計劃很完善。
17）It's my turn. 該輪到我了。
it也常用於某些習慣用語中作賓語，各該習慣用語有具體意義，但it並無具體意義。如：
cab it 乘車 catch it 受責，受罰 come it 儘自己分內 come it strong 做得過分 walk it 步行 make it 辦成 take it out of somebody 拿某人出氣
4. 先行詞it.
it充當形式主語或形式賓語，本身無意義，只起一種先行引導的作用，先行詞不重讀。後面的真正主語或真正賓語通常是不定式結構、-ing分詞結構或名詞性從句。
（1）用作形式主語
18）It is difficult to translate this article. 翻譯這篇文章很難。
19）It is getting harder every day for a lazy man to get a living. 懶漢謀生是日益困難了。
20）What time would it be most convenient for me to call again?什麼時候我再給你打電話最合適？
21）It is no use going there so early. 這麼早去那裡沒有用。
22）It has been a great honour your coming to visit me. 你的來訪是我很大的榮幸。
23）It is strange that he did not come at all. 真奇怪，他竟還沒來。
24）It doesn't matter what you do.什麼都沒關係。
在上述諸例中，後置的真正主語可以取代先行it的位置，而出現於句首。
To translate this article is difficult.
Going there so early is no use.
That he did not come at all is strange.
上述結構遠不如用先行it結構普通。此外，也並非所有先行it結構都可作上述轉換。如：
25）It seems that John is not coming after all. 似乎約翰終竟不來。
26）It happened that John was the only witness. 碰巧約翰是唯一的證人。
上述兩例只能轉換為：
John doesn't seem to be coming after all.
John happened to be the only witness.
（2）用作形式賓語
27）I found it difficult to explain to him what happened. 我覺得向他解釋清發生了什麼事很困難。
28）He thought it no use going over the subject again. 他認為再討論這個問題沒有用了。
29）They kept it quiet that he was dead. 他們對他的死保密。
30）We must make it clear to the public that something should be done to stop pollution.我們必須使公眾明白應該採取措施制止污染。
分裂句引導詞it.
分裂句是以it為引導詞的強調句型。它的結構形式是：It+be的一定形式+中心成分+that-/who-從句。如：
31）It was Jane that/who called this morning. 是珍妮今天上午打來電話。
32）It was a parcel that she brought him. 她帶給他的是一個包裹。
分裂句是由普通陳述句轉換而來的。通過這種結構可以強調除謂語動詞以外的大多數句子成分。如：
33）John gave Mary a handbag at Christmas. 約翰在聖誕節給了瑪麗一個提包。
根據上下文和語義意圖，說話人可以通過分裂句分彆強調主語、間接賓語、直接賓語、狀語，使之成為信息中心。
34）It was John that/who gave Mary a handbag at Christmas. 是約翰在聖誕節給了瑪麗一個提包。
35）It was Mary that John gave a handbag （to） at Christmas. 約翰在聖誕節是給瑪麗提包的。
36）It was a handbag that John gave Mary at Christmas. 約翰在聖誕節給瑪麗的是一個提包。
37）It was at Christmas that John gave Mary a handbag. 是在聖誕節約翰給了瑪麗一個提包。
分裂句的時態一般應一致，即主句與從句的時態應皆用現在時，或皆用過去時，或皆用將來時。如：
38）It is not I who am angry. 發怒的不是我。
39）It was my two sisters who knew her best. 是我的兩個姐妹最了解她。
40）It will not be you who will have to take the blame for this. 對此須受責難的將不是你。
有時分裂句的謂語動詞還可以採取複雜形式。如：
41）It may have been at Christmas that John gave Mary a handbag. 可能是在聖誕節約翰給瑪麗一個提包。
42）It might have been John who gave Mary a handbag. 很可能是約翰給了瑪麗一個提包。
分裂句可以強調多種多樣的狀語成分。如：
43）It was when she was about to go to bed that the telephone rang. 是在她即將上床睡覺時電話鈴響了。
44）It was because I wanted to buy a dictionary that I went to town yesterday. 我昨天是由於想買一本詞典而進城的。
45）It was not until his father came back that Tom went to bed yesterday.
昨天湯姆是直到他父親回來才上床睡覺的。（注意句中not的位置）
主語補語通常不可以用作分裂句的中心成分，如在規範英語中通常不說：
It is beautiful that she is.
It is chairman of the Committee that he is.
但是賓語補語是可以這樣用的。如：
46）It is the chairman of the committee that they elected him. 他們選他是作委員會主席。
47）It is green that they have painted the wall. 他們把牆壁漆的是綠色。
註：（1）當強調的中心成分為主語，指人時可用連詞that或who，如上述例（31）、（34）、（38），強調其餘的成分時，連詞一律用that。
（2）分裂句中的that與who在非正式文體中可以省略，如：
48）It was the President himself spoke to me.是總統親自和我談了話。（省去從句主語who）
49）It was the dog I gave the water to. 我是給那條狗水的。（省去從句的賓語that）
50）It was yesterday I first noticed it. 我是昨天開始注意到的。（省去從句連詞that）
有時還可省去句首的it is，如：
51）A good, honest trade you are learning, Sir Peter! 彼得爵士，你學得是一種很好而誠實的一行啊！
（3）分裂句中的被強調部分有時可放在句首，如：
52）Now was it that his life was done, and the fate which he could not escape was upon him.就在這時，他的生命完結了，他所逃不脫的命運降臨了。
53）When was it that he arrived at the village? 是何時他到達了這個村子？
54）Why was it that he was late for school? 他是為什麼上學遲到的？
1. 分裂句引導詞it與先行詞it的區別： 比較：
55）It is surprising that Mary should have won the first place. 瑪麗本應獲得第一名，真令人吃驚！（先行詞it）
56）It is Mary that has won the first place. 是瑪麗獲得了第一名。（分裂句引導詞it）
2. 虛義it與分裂句引導詞it的區別。 比較：
57）It was three o'clock in the morning when his father came back.（虛義it指時間） 他父親回來時是凌晨3點。
58）It was at three o'clock in the morning that his father came back. （分裂句引導詞it） 他父親是在凌晨3點回來的。
3. 分裂句中that/who- 從句與that/who引導的定語從句之區別。 比較：
59）It is money that is most needed.（分裂句中的that-從句） 最需要的是錢。
60）This is the money that is most needed.（that引導定語從句） 這就是最需要的錢。
61）It is Mary who has broken the glass （分裂句中的who-從句） 是瑪麗打破了玻璃杯。
62）Mary is the girl who has won the first place.（who引導定語從句） 瑪麗是獲得第一名的姑娘。
區別方法：如將句型It is/was…that結構去掉，而句子能還原成普通陳述句，則該句是分裂句，否則不是。如（56）例去掉It is …that
則變成： Mary has won the first place. 瑪麗獲得了第一名。
（58）例變成：His father came back at three o'clock in the morning. 他父親在凌晨3點回來。
（59）例變成：Money is most needed. 錢是最需要的。
（61）例變成：Mary has broken the glass. 瑪麗打破了玻璃杯。
4. “擬似”分裂句
如前所述，一般分裂句是不可以用簡單陳述句的謂語動詞作為中心成分的。如果要強調謂語動詞，就得採用另外一種強調句型，這種句型又叫做“擬似”分裂句。如：
63）I gave her a book.
What I did was （to） give her a look. 我所做的是給她一本書。
64）He took a plane to Beijing. What he did was （to） take a plane to Beijing. 他所做的是乘飛機去北京。
65）The student is going to write an article.
What the student is going to do is（to） write an article.這個學生要做的是寫一篇文章。
“擬似”分裂句的主語通常是由what引導的名詞性從句，從句的主動詞通常是do的一定形式；這種分裂句的主語補語通常是不定式結構，可帶to，也可不帶to，它構成“擬似”分裂句的信息中心。
“擬似”分裂句還可採取另外一種形式，即“what-從句+be+名詞詞組”的形式，如：
66）What he gave her was a handbag. 他所給她的是個提包。
也可採取“名詞詞組+be+what-從句”的形式
67）A handbag was what he gave her. 提包就是他所給她的。
鞏固練習：
1. 用先行詞it改寫下列句子：
（1）Possibly the Joneses will come to the party as well.
（2）Whether they will come or not doesn't matter very much.
（3）He is quite likely to let you down.
（4）You seem to have taken a dislike to him.
（5）I happen to have had some nasty experiences in dealing with him.
（6）Getting the car on the boat was rather complicated.
（7）To be with you here this evening is a great pleasure.
（8）You were so kind to invite us.
（9）What you say does not matter in the least.
（10）How he came to have such a valuable painting is a mystery.
2. 翻譯下列句子：
（1）冬天，天色晚得早。
（2）問她沒有用，她什麼也不知道。
（3）從這兒到車站有兩英里（路程）。
（4）你見過下冰雹嗎？
（5）由你來決定該怎麼辦？
（6）據說他已去過美國兩次了。
（7）可惜你錯過了那次音樂會。
（8）看來，他很害怕。
（9）牛奶已經潑翻，哭也無用。（即：作無益的後悔無濟於事。）
（10）幾個月之後我們才又見面。
3. 用強調句型改寫下列句子。（劃線部分為中心成分）
（1）She has been studying French only for three months.
（2）He has painted the windows green.
（3）John bought the car from Henry.
（4）I met Henry in New York.
（5）He didn't come home until 11 o'clock last night.
翻譯句子答案：
（1）It is getting dark earlier in winter.
（2）It is no use asking her because she didn't know anything about it.
（3）It's two miles from here to the bus station.
（4）Have you seen it hailing?
（5）It is up to you decide what to do.
（6）It is said that he has been to the U.S.A. twice.
（7）It's a pity that you've missed the concert.
（8）It seems that he is much afraid.
（9）It's no use crying over spilt milk.
（10）It was several months before we met again.
1. 人稱代詞it，是第三人稱單數中性，代表前文已提到過的一件事物。如：
1）That vase is valuable. It's more than 200 years old. 那個花瓶很珍貴，它有200多年的歷史。
2）I love swimming. It keeps me fit. 我喜歡游泳，它能使我保持健康。
當說話者不清楚或無必要知道說話對象的性別時，也可用it來表示。 如：
3）It's a lovely baby. Is it a boy or a girl? 寶寶真可愛，是男孩還是女孩？
it可用來指代團體。如：
4）The committee has met and it has rejected the proposal. 委員會已開過會，拒絕了這項建議。
it用以代替指示代詞this, that.如：
5）--- What's this? --- It's a pen. —這是什麼？ —是一支鋼筆。
6）--- Whose book is that? --- It's Mike's. —那是誰的書？ —是邁克的。
2. 指示代詞it，常用以指人。如：
7）Go and see who it is. 去看看是誰。
8）--- Who is making such a noise? —是誰發出這樣的吵鬧聲？
--- It must be the children. —一定是孩子們。
3.虛義it無指代性，常用作沒有具體意義的主語，出現於表示天氣、氣候、溫度、時間、地點、距離等意義的句子中。如：
9）It is half past three now. 現在是三點半鐘。
10）It is six miles to the nearest hospital from here. 這裡離最近的醫院也有六英里。
11）It was very cold; it snowed and grew dark.
天氣很冷；天下著雪，漸漸地變黑了。
it也常用來表示一般的籠統的情況。如：
12）It's awful—I've got so much work I don't know where to start. 糟透了——我有這麼多工作要做我不知從何開始。
13）How is it going with you? 你近況如何？
14）Take it easy. 不要緊張。
it也常用於下列結構：
15）It looks as if the college is very small. 看起來這個學院很小。
16）It seems as though our plan will be perfect. 似乎我們的計劃很完善。
17）It's my turn. 該輪到我了。
it也常用於某些習慣用語中作賓語，各該習慣用語有具體意義，但it並無具體意義。如：
cab it 乘車 catch it 受責，受罰 come it 儘自己分內 come it strong 做得過分 walk it 步行 make it 辦成 take it out of somebody 拿某人出氣
4. 先行詞it.
it充當形式主語或形式賓語，本身無意義，只起一種先行引導的作用，先行詞不重讀。後面的真正主語或真正賓語通常是不定式結構、-ing分詞結構或名詞性從句。
（1）用作形式主語
18）It is difficult to translate this article. 翻譯這篇文章很難。
19）It is getting harder every day for a lazy man to get a living. 懶漢謀生是日益困難了。
20）What time would it be most convenient for me to call again?什麼時候我再給你打電話最合適？
21）It is no use going there so early. 這麼早去那裡沒有用。
22）It has been a great honour your coming to visit me. 你的來訪是我很大的榮幸。
23）It is strange that he did not come at all. 真奇怪，他竟還沒來。
24）It doesn't matter what you do.什麼都沒關係。
在上述諸例中，後置的真正主語可以取代先行it的位置，而出現於句首。
To translate this article is difficult.
Going there so early is no use.
That he did not come at all is strange.
上述結構遠不如用先行it結構普通。此外，也並非所有先行it結構都可作上述轉換。如：
25）It seems that John is not coming after all. 似乎約翰終竟不來。
26）It happened that John was the only witness. 碰巧約翰是唯一的證人。
上述兩例只能轉換為：
John doesn't seem to be coming after all.
John happened to be the only witness.
（2）用作形式賓語
27）I found it difficult to explain to him what happened. 我覺得向他解釋清發生了什麼事很困難。
28）He thought it no use going over the subject again. 他認為再討論這個問題沒有用了。
29）They kept it quiet that he was dead. 他們對他的死保密。
30）We must make it clear to the public that something should be done to stop pollution.我們必須使公眾明白應該採取措施制止污染。
分裂句引導詞it.
分裂句是以it為引導詞的強調句型。它的結構形式是：It+be的一定形式+中心成分+that-/who-從句。如：
31）It was Jane that/who called this morning. 是珍妮今天上午打來電話。
32）It was a parcel that she brought him. 她帶給他的是一個包裹。
分裂句是由普通陳述句轉換而來的。通過這種結構可以強調除謂語動詞以外的大多數句子成分。如：
33）John gave Mary a handbag at Christmas. 約翰在聖誕節給了瑪麗一個提包。
根據上下文和語義意圖，說話人可以通過分裂句分彆強調主語、間接賓語、直接賓語、狀語，使之成為信息中心。
34）It was John that/who gave Mary a handbag at Christmas. 是約翰在聖誕節給了瑪麗一個提包。
35）It was Mary that John gave a handbag （to） at Christmas. 約翰在聖誕節是給瑪麗提包的。
36）It was a handbag that John gave Mary at Christmas. 約翰在聖誕節給瑪麗的是一個提包。
37）It was at Christmas that John gave Mary a handbag. 是在聖誕節約翰給了瑪麗一個提包。
分裂句的時態一般應一致，即主句與從句的時態應皆用現在時，或皆用過去時，或皆用將來時。如：
38）It is not I who am angry. 發怒的不是我。
39）It was my two sisters who knew her best. 是我的兩個姐妹最了解她。
40）It will not be you who will have to take the blame for this. 對此須受責難的將不是你。
有時分裂句的謂語動詞還可以採取複雜形式。如：
41）It may have been at Christmas that John gave Mary a handbag. 可能是在聖誕節約翰給瑪麗一個提包。
42）It might have been John who gave Mary a handbag. 很可能是約翰給了瑪麗一個提包。
分裂句可以強調多種多樣的狀語成分。如：
43）It was when she was about to go to bed that the telephone rang. 是在她即將上床睡覺時電話鈴響了。
44）It was because I wanted to buy a dictionary that I went to town yesterday. 我昨天是由於想買一本詞典而進城的。
45）It was not until his father came back that Tom went to bed yesterday.
昨天湯姆是直到他父親回來才上床睡覺的。（注意句中not的位置）
主語補語通常不可以用作分裂句的中心成分，如在規範英語中通常不說：
It is beautiful that she is.
It is chairman of the Committee that he is.
但是賓語補語是可以這樣用的。如：
46）It is the chairman of the committee that they elected him. 他們選他是作委員會主席。
47）It is green that they have painted the wall. 他們把牆壁漆的是綠色。
註：（1）當強調的中心成分為主語，指人時可用連詞that或who，如上述例（31）、（34）、（38），強調其餘的成分時，連詞一律用that。
（2）分裂句中的that與who在非正式文體中可以省略，如：
48）It was the President himself spoke to me.是總統親自和我談了話。（省去從句主語who）
49）It was the dog I gave the water to. 我是給那條狗水的。（省去從句的賓語that）
50）It was yesterday I first noticed it. 我是昨天開始注意到的。（省去從句連詞that）
有時還可省去句首的it is，如：
51）A good, honest trade you are learning, Sir Peter! 彼得爵士，你學得是一種很好而誠實的一行啊！
（3）分裂句中的被強調部分有時可放在句首，如：
52）Now was it that his life was done, and the fate which he could not escape was upon him.就在這時，他的生命完結了，他所逃不脫的命運降臨了。
53）When was it that he arrived at the village? 是何時他到達了這個村子？
54）Why was it that he was late for school? 他是為什麼上學遲到的？
1. 分裂句引導詞it與先行詞it的區別： 比較：
55）It is surprising that Mary should have won the first place. 瑪麗本應獲得第一名，真令人吃驚！（先行詞it）
56）It is Mary that has won the first place. 是瑪麗獲得了第一名。（分裂句引導詞it）
2. 虛義it與分裂句引導詞it的區別。 比較：
57）It was three o'clock in the morning when his father came back.（虛義it指時間） 他父親回來時是凌晨3點。
58）It was at three o'clock in the morning that his father came back. （分裂句引導詞it） 他父親是在凌晨3點回來的。
3. 分裂句中that/who- 從句與that/who引導的定語從句之區別。 比較：
59）It is money that is most needed.（分裂句中的that-從句） 最需要的是錢。
60）This is the money that is most needed.（that引導定語從句） 這就是最需要的錢。
61）It is Mary who has broken the glass （分裂句中的who-從句） 是瑪麗打破了玻璃杯。
62）Mary is the girl who has won the first place.（who引導定語從句） 瑪麗是獲得第一名的姑娘。
區別方法：如將句型It is/was…that結構去掉，而句子能還原成普通陳述句，則該句是分裂句，否則不是。如（56）例去掉It is …that
則變成： Mary has won the first place. 瑪麗獲得了第一名。
（58）例變成：His father came back at three o'clock in the morning. 他父親在凌晨3點回來。
（59）例變成：Money is most needed. 錢是最需要的。
（61）例變成：Mary has broken the glass. 瑪麗打破了玻璃杯。
4. “擬似”分裂句
如前所述，一般分裂句是不可以用簡單陳述句的謂語動詞作為中心成分的。如果要強調謂語動詞，就得採用另外一種強調句型，這種句型又叫做“擬似”分裂句。如：
63）I gave her a book.
What I did was （to） give her a look. 我所做的是給她一本書。
64）He took a plane to Beijing. What he did was （to） take a plane to Beijing. 他所做的是乘飛機去北京。
65）The student is going to write an article.
What the student is going to do is（to） write an article.這個學生要做的是寫一篇文章。
“擬似”分裂句的主語通常是由what引導的名詞性從句，從句的主動詞通常是do的一定形式；這種分裂句的主語補語通常是不定式結構，可帶to，也可不帶to，它構成“擬似”分裂句的信息中心。
“擬似”分裂句還可採取另外一種形式，即“what-從句+be+名詞詞組”的形式，如：
66）What he gave her was a handbag. 他所給她的是個提包。
也可採取“名詞詞組+be+what-從句”的形式
67）A handbag was what he gave her. 提包就是他所給她的。
鞏固練習：
1. 用先行詞it改寫下列句子：
（1）Possibly the Joneses will come to the party as well.
（2）Whether they will come or not doesn't matter very much.
（3）He is quite likely to let you down.
（4）You seem to have taken a dislike to him.
（5）I happen to have had some nasty experiences in dealing with him.
（6）Getting the car on the boat was rather complicated.
（7）To be with you here this evening is a great pleasure.
（8）You were so kind to invite us.
（9）What you say does not matter in the least.
（10）How he came to have such a valuable painting is a mystery.
2. 翻譯下列句子：
（1）冬天，天色晚得早。
（2）問她沒有用，她什麼也不知道。
（3）從這兒到車站有兩英里（路程）。
（4）你見過下冰雹嗎？
（5）由你來決定該怎麼辦？
（6）據說他已去過美國兩次了。
（7）可惜你錯過了那次音樂會。
（8）看來，他很害怕。
（9）牛奶已經潑翻，哭也無用。（即：作無益的後悔無濟於事。）
（10）幾個月之後我們才又見面。
3. 用強調句型改寫下列句子。（劃線部分為中心成分）
（1）She has been studying French only for three months.
（2）He has painted the windows green.
（3）John bought the car from Henry.
（4）I met Henry in New York.
（5）He didn't come home until 11 o'clock last night.
翻譯句子答案：
（1）It is getting dark earlier in winter.
（2）It is no use asking her because she didn't know anything about it.
（3）It's two miles from here to the bus station.
（4）Have you seen it hailing?
（5）It is up to you decide what to do.
（6）It is said that he has been to the U.S.A. twice.
（7）It's a pity that you've missed the concert.
（8）It seems that he is much afraid.
（9）It's no use crying over spilt milk.
（10）It was several months before we met again.
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