用一個句子作狀語,這個句子就是狀語從句。狀語從句通常用來修飾句子、動詞或形容詞,表示時間、地點、條件、原因、目的、結(jié)果、方式、比較等。引導(dǎo)狀語從句的連詞叫從屬連詞。
在句中相當于時間狀語的從句叫時間狀語從句。時間狀語從句常由從屬連詞when,while,as,before,after,as soon as,since,till,until等引導(dǎo)。如:
What are you going to be when you grow up ?你長大以后打算干什么?
I will phone you as soon as I get there .我一到那兒就給你打電話。
1.引導(dǎo)時間狀語從句的從屬連詞及用法
(1)when,while,as引導(dǎo)時間狀語從句意為“當……時”。如:
When the clock struck twelve ,all the lights went out.當時鐘敲了十二下,燈全部都熄了。
While Peter was reading ,his wife was cooking.彼得看書的時候,他妻子在做飯。
He dropped the glass as he stood up .他站起來時,把杯子摔碎了。
注意:
①when表示“當……時”,多用來表示時間點,也可表示時間段;從句中既可以用非延續(xù)性動詞,也可用延續(xù)性動詞;when 從句多用一般過去時,主句時態(tài)沒有限制,根據(jù)具體情況而定;在將來時態(tài)中,常用when引導(dǎo)從句,且從句須用一般現(xiàn)在時代替將來時;when表示時間段時可與while通用,但從句中必須用延續(xù)性動詞。如:
I was just reading a book when she came into my room.她走進我房間時,我正在看書。
When I got to the airport,the guests had left.當我趕到飛機場時,客人們已經(jīng)離開了。
When the manager comes here for a visit next week,I'll talk with him about this.下周經(jīng)理來這參觀時,我會和他談?wù)劥耸隆?/p>
②while表示“當……的時候;在……之時;在……期間”,所引導(dǎo)的時間狀語從句的謂語動詞必須是延續(xù)性動詞或表示狀態(tài)的動詞,且通常用進行時。如:
While my wife was reading the newspaper,I was watching TV.當妻子在看報紙的時候,我在看電視。
You can't do your homework while you're watching TV.你不能一邊看電視一邊做家庭作業(yè)。
③as引導(dǎo)時間狀語從句時,從句的謂語動詞既可以是延續(xù)性的,也可以是非延續(xù)性的。當從句中的謂語動詞是延續(xù)性動詞,表示“當……的時候”時,往往可以與when或while通用,但as更側(cè)重主句與從句的行為同時發(fā)生,常譯作“隨著……;一邊……,一邊……”。如:
Kate read the book as she went along.凱特邊走邊讀書。
We took notes as we listened to the lecture.我們邊聽課邊記筆記。
(2)before引導(dǎo)時間狀語從句意為“在……之前”。如:
Don't jump off the train before it stops.火車停之前不要往下跳。
Look at both ways before you cross the road.過馬路之前左右兩邊都要看。
I didn't know any English before I came here。我來這兒之前,一點英語都不懂。
(3)after引導(dǎo)時間狀語從句意為“在……之后”。如:
I'll have a walk after I finish my work.我做完事后要去散步。
After he locked the door,he left.他鎖上門之后就走了。
注意:
為了表明動作的先后,從句中動詞可用過去完成時,主句用一般過去時。如:
After he had finished his work,he played a game of chess with his friends.他做完工作后,和朋友下了一會兒棋。
(4)until,till引導(dǎo)時間狀語從句意為“直到……為止”。如:
They waited till/until I returned.他們一直等到我回來。
Mr.Wang kept on explaining until the student understood.王先生反復(fù)地解釋直到學(xué)生聽懂了為止。
注意:
①until在肯定句中只與延續(xù)性動詞連用,在否定句中通常與非延續(xù)性動詞連用,表示相應(yīng)動作開始的時間,意為“直到……才”。如:
He didn't leave until I came back.直到我回來他才離開。
②till用作連詞,與until同義,兩者經(jīng)常可換用,只是 until 比 till 稍正式。在正式文體中,一般用 until,而在口語或非正式文體中則兩者都可。till多與名詞或較短的從句連用,而較長較復(fù)雜的成分多用 until;在句子開頭時,用 until而不用till。如:
She lived in Tokyo till (until)she died.她一直住在東京直到去世。
(√)Until he comes back,nothing can be done.在他回來之前,什么也不能做。
(×)Till he comes back,nothing can be done.在他回來之前,什么也不能做。
(5)since引導(dǎo)時間狀語從句意為“自……以來”
Since I left school,I have written to him twice.自從我離開學(xué)校以來,我已經(jīng)給他寫過兩封信。
I have not heard from him since he left Shanghai.自從他離開上海以來,我就沒有收到過他的來信。
注意:
since引起的時間狀語從句通常用一般過去時態(tài),主句用現(xiàn)在完成時態(tài)。如:
I've worked here since I left school.自我離開學(xué)校以來我一直在這里工作。
(6)as soon as引導(dǎo)時間狀語從句意為“一……就……”
I'll tell you as soon as I get here.我一到這里就告訴你。
I want to see him as soon as he arrives.他一到我就想見他。
2.時間狀語從句的時態(tài)
(1)當主句的謂語動詞是一般將來時,由when,before,after,as soon as,until 等連詞引導(dǎo)的時間狀語從句用一般現(xiàn)在時。如:
I 'll tell him the good news as soon as I see him.我一見到他,就告訴他這個好消息。
The boy will be a writer when he grows up.這個男孩長大后將成為一名作家。
(2)當主句的謂語含有can,may,must等情態(tài)動詞時,由when,before,after,until,as soon as等引導(dǎo)的時間狀語從句用一般現(xiàn)在時。如:
You can go home after you finish your homework.你做完作業(yè)后就可以回家。
When the lights are red,the traffic must stop .紅燈亮?xí)r,車輛必須停下。
You may wait here before your father comes .在你父親到來之前你可以在這兒等著。
(3)當主句的謂語是want,hope,wish等動詞的一般現(xiàn)在時形式時,由when,before,after,until,as soon as等引導(dǎo)的時間狀語從句用一般現(xiàn)在時。如:
He wants to be a doctor when he grows up.他長大后想當一名醫(yī)生。
She wants to work in America when she finishes college.她大學(xué)畢業(yè)后想在美國工作。
(4)當主句是祈使句時,由when,before,after,until等引導(dǎo)的時間狀語從句用一般現(xiàn)在時。如:
Don't get off the bus until it stops .公共汽車停下來再下車。
Please don't go to bed before you finish your homework.在完成作業(yè)之前,請不要睡覺。
(5)當主句謂語用一般過去時,由when,before,after,until,as soon as等引導(dǎo)的時間狀語從句也要用一般過去時。如:
They talked about the party after people left .人們離開后,他們談?wù)撨@次晚會情況。
(6)當before引導(dǎo)的時間狀語從句是過去時態(tài),主句一般用過去完成時,有時也用一般過去時。如:
She had learned Japanese for three years before she went to Japan.她去日本之前學(xué)了三年日語。
She didn't know me before she came here.她到這里來之前不認識我。
(7)since引導(dǎo)的時間狀語從句要用一般過去時,主句的謂語動詞要用延續(xù)性動詞,通常用現(xiàn)在完成時;用非延續(xù)性動詞時,要用否定式。如:
He has waited here since you left .自從你走之后他一直在這等著。
He hasn't gone to the school since he finished the school.他畢業(yè)后再沒去過學(xué)校。
注意:
在It is+時間+since從句結(jié)構(gòu)中,主句用一般現(xiàn)在時,從句用一般過去時。如:
It is three years since I began to study English.我開始學(xué)英語已經(jīng)有三年了。
3.時間狀語從句的位置
(1)when,before,after,as,while,as soon as等引導(dǎo)的時間狀語從句的位置可位于句首,也可位于句末。放在句首時,從句后通常用逗號與主句隔開,放在句末時,從句與主句之間一般不用逗號,只在句末用句號或問號。如:
When you came to see me,I was ready to leave.你來看我時,我正準備離開。
You called me while I was watching TV.我在看電視時,你給我打了電話。
After she cleaned the classroom,she went home.她打掃完教室后回家了。
(2)since引起的時間狀語從句通常放在主句的后面。
I have learned English since I came to this school.我自從來到這個學(xué)校以來就一直在學(xué)英語。
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