包含條件從句的句子都是條件句,有些條件句是可能實現(xiàn)的,如:
If I have time I'll come over to see you. 如果我有時間我就來看你。
If we leave now, we can still catch the train. 如果我們現(xiàn)在動身,還可能趕上火車。
I won't go to the party unless they invite me. 除非他們邀請我,否則我不會參加這個晚會。
If you are waiting for a bus you'd better join the queue. 如果你是在等車,你最好排隊。
If he has written the letter, I'll post it. 如果他已把信寫好,我就去發(fā)。
這種條件句稱為真實條件句(Sentences of Real Condition)。另有一些條件句表示純?nèi)患傧氲那闆r,稱為虛擬條件句(Sentences of Unreal Condition),在這類條件句中謂語動詞就需要用虛擬語氣:
If I had enough money, I would buy a computer. 如果我有足夠的錢,我將買一臺電腦。(但我沒有)
If you had arrived a little earlier, you would have seen her. 你要是早來一會兒就見到她了。
1) 表示現(xiàn)在或?qū)砬闆r的虛擬條件句,動詞形式可以下表表示:
這類句子或表示與事實相反的情況或?qū)崿F(xiàn)可能性不大的情況:
If I had a map I would lend it to you. 如果我有地圖我就借給你。(但我沒有)
If you left your bicycle outside, someone would steal it. 如果你把自行車放在外邊,有人會偷的。(當然你不會這樣做)
If I dyed my hair blue everyone would laugh at me. 如果我把頭發(fā)染成藍色,誰都會笑我的。(當然我不會干這樣的傻事)
If I lived near my office, I'd walk to work. 如果我住在辦公室附近,我就會步行上班。
If I were you I'd plant some trees round the house. 如果我是你,我會在房子周圍種些樹。
If Helen were (was) here how nice it would be! 海倫要是在這里該多好!
在If I were you這樣的句子中,were不能改成was,但在第三人稱單數(shù)后(如最后一句)用was也可以。
2) 在主句中謂語有時也可由might, could構(gòu)成:
If you tried again you might succeed. 如果再試一次,你可能會成功。
If I could type, I might save a lot of time. 如果我會打字,我可能會節(jié)省大量時間。
If I knew her number I could ring her up. 我要是知道她的號碼我就能給她打電話。
If he had a permit he could get a job. 如果他有許可證,他可以找到一份工作。
3) 在條件從句中有時還可以用“were to+不定式”(a)或“should+不定式”(b)這兩種形式:
a. If he were (was) to resign, who would take his place? 如果他要辭職,誰來接替他?
If I were to do the job, I would do it in a different way. 要是我來做這工作,我會是另一種做法。
b. If you should have any difficulty in getting the medicine, (you could) ringthis number. 如果你找這種藥有困難,你可以撥打這個電話。
If the toys should arrive in a damaged condition, please inform us at once.如果這些玩具運到時有損壞,請立即通知我們。
在后面這類句子中,主句的謂語有時可用祈使語氣(見上例),或用陳述語氣:
If I should be free tomorrow, I will come to see you. 如果明天我有空我會來看你的。
4) 在某些條件從句(如包括were和should的從句)中,if有時可省略,這時語序要改為倒裝:
Were I Tom I would refuse. 如果我是湯姆我會拒絕。
Were I in your shoes I would let him know what I thought of him. 如果我處于你的地位,我會讓他知道我對他的看法。
Should you require anything just give me a ring. 你要是需要什么就給我打個電話。
Should she be interested, I'll phone her. 如果她有興趣,我會給她打電話。
5) 從句有時可用If it were not for這種句型,表示“若不是”:
If it weren't for your help, we would be in serious trouble. 若不是你幫忙,我們會遇到大麻煩。
Were it not for their loan, our life would be very difficult. 要不是有他們的貸款,我們的生活會很困難。
You wouldn't be anywhere if it weren't for Ruth. 要不是露絲你不會有任何成就。
6) 在極少情況下,從句中的謂語可用動詞原形,主句中的謂語可用陳述語氣:
If any person be found guilty, he shall have the right of appeal. 如果有人被判定有罪,他應(yīng)有上訴權(quán)。
If that be the official view, it cannot be accepted. 如果這是官方的看法,這是不能接受的。
If any vehicle be found parked on these premises, it shall be towed away.如果發(fā)現(xiàn)有車停在此處,它將被拖走。
這是比較大氣的說法,口語中很少使用。
1) 表示過去情況的虛擬條件句動詞形式可以下表表示:
這類從句表示一個與事實相反的過去情況('d是had/would的緊縮形式):
If I had known that you were coming, I would have met you at the airport.如果我知道你要來,我就會去機場接你了。(但我不知道)
If anything had happened, he would have let us know. 如果發(fā)生了什么情況,他早就通知我們了。(想必沒發(fā)生什么事)
She would have said more if he had not walked away. 如果他沒走開,她還會多說些話的。
If I had left sooner, I'd have caught the bus. 如果早點動身,我就趕上巴士了。
If I had been Nancy, I wouldn't have left him. 我要是南希,我不會離開他。
What would you have done if you'd been in my position? 如果你處于我的位置你會怎么辦?
在主句中,如果主語是第一人稱,也有人用should構(gòu)成謂語:
I should (would) have talked to mother if I had thought of it. 如果我想起了那事,我是會向母親談及的。
I should (would) never have done it if I hadn't been so hard up. 如果手頭不是那樣拮據(jù),我是不會那樣做的。
2) 主句中也可用could和might構(gòu)成謂語:
No doubt I could have earned something if I had really meant to. 如果我有心掙點錢,我肯定能掙到一些的。
If my father had lived, he could have done all this for me. 如果我父親活著,這一切他都會幫我做的。
If I had been less cautious, I might have been more wise. 如果我少一些謹慎,也許就會多一些明智。
If we had found him earlier we might have saved his life. 如果我們早點找到他,我們或許已把他救活了。
有時還可由should(應(yīng)當)構(gòu)成:
If he had received the present, he should have thanked her. 如果他收到了禮物,他是應(yīng)當向她道謝的。
If he had apologized, you should have done so too. 如果他道歉了,你也應(yīng)當這樣做。
3) 從句中也可用had not been for來構(gòu)成謂語,表示“要不是”
If it hadn't been for your timely help, we would have got into serious trouble.要不是你及時幫助,我們會陷入嚴重的困境。
If it hadn't been for her meticulous care, I wouldn't have got well so soon.要不是有她精心的照顧,我不會好得這樣快。
If it hadn't been for Margaret, I might not have understood. 要不是有瑪格麗特,我也許不會明白的。
4) if有時可以省略,但后面部分需改為倒裝語序:
Had she been asked, she would have done it. 如果那時請她做,她是會做的。
Had I not seen it with my own eyes, I would not have believed it. 這事要不是我親眼所見,我都不會相信的。
Had it not been for their support, we couldn't have won the election. 要不是有他們的支持我們不可能贏得選舉。
Had Mark been in charge, it wouldn't have happened. 如果是馬可負責,這事就不會發(fā)生了。
1) 錯綜時間條件句:
有些條件句主句謂語和從句謂語表示的動作在時間上并不一致,這類句子稱為錯綜時間條件句(Conditional Sentences of Mixed Time),如:
If the weather had been more favourable, the crops would be growing still better. 如果前些時候天氣好一點,莊稼現(xiàn)在會長得更好。
If he had received six more votes, he would be our chairman now. 他要是多得六票,現(xiàn)在就是我們的主席了。
If you had taken her advice, you wouldn't be in such trouble now. 如果你聽了她的勸告,你現(xiàn)在就不會有這種麻煩。
If it hadn't been for the doctors' care, I wouldn't be speaking to you now.要不是有醫(yī)生們的照顧,我此時不會在和你說話。
If he were leaving, you would have heard about it. 如果他真的要走,你早就聽到消息了。
If he had been trying hard, her parents wouldn't be so worried. 如果她一直很努力,她的父母也不會這樣著急了。
2) 含蓄條件句:
有些句子雖不含條件從句,但意思和條件句差不多,這種句子稱為含蓄條件句(Sentences of Implied Condition),在這種句子中也可能需用虛擬語氣:
I might see her personally, it would be better. 我可能親自去見她,這樣會好一些。
I would have written before but I have been ill. 要不是病了,我早給你寫信了。
But for my money that woman would have persecuted him. 若不是我花了錢那女人早就找上他的麻煩了。
I did not press the point as it would have been useless. 我沒有堅持這一點,因為堅持也沒用。
In the old days she would have argued. 要是在過去她早就爭論上了。
Such a thing wouldn't have happened elsewhere. 這樣的事別處是不會發(fā)生的。
Anybody else would have believed you. 要換上別人早就信了你的話。
To have told my secret would have given me away. 講出了我的秘密就等于出賣了我。
I wouldn't worry about it. It wouldn't do any good. 我不會為此發(fā)愁,這樣沒好處。
She would have done anything to make amends. 她愿做任何事來賠罪。
3) 某些情態(tài)動詞的使用:
某些情態(tài)動詞,特別是should, would, could, might,在口語中用得很多,使語氣變得客氣委婉:
Would you mind shutting the window? 勞駕把窗子關(guān)上好嗎?
Would you tell me how to get to the tube? 可否請告訴我怎么去地鐵站?
When would it be convenient for you to begin? 你何時開始比較方便?
Seattle wouldn't suit her. 西雅圖不會適合她的。
I'd go there with you. 我將和你一道去。
I should be glad to talk to him. 我愿和他談?wù)劇?
I should think you would be above anything like that. 我想你不會做出這樣的事來。
I should find it very hard to believe. 我會覺得這難以置信。
I should have preferred him to do it in a different way. 我倒寧愿他以另一種方式來處理此事。
Could you lend me your computer? 你可否把電腦借我用一下?
I could come earlier, if necessary. 如有必要我可以早點來。
No one could be more generous;he has a heart of gold. 誰也沒他慷慨;他有一顆金子般的心。
Might I ask for a photograph of Mr. Strakov? 我可否要一張斯特拉可夫先生的照片?
If necessary, you might shorten it. 必要的話你可以把它縮短。
I might have come to a wrong conclusion. 我也許得出了錯誤的結(jié)論。
這類句子的謂語雖不一定是虛擬語氣,卻很接近虛擬語氣。一是它們在形式上和虛擬條件句中的謂語形式很相近;二是它們不受時態(tài)的限制,現(xiàn)在情況可以過去形式表示;三是和一般陳述語氣有些差異,更帶主觀色彩。因此,說它們是虛擬語氣或接近虛擬語氣也未嘗不可。