、虛擬條件句的三種基本類型：與現(xiàn)在事實相反、與過去事實相反、與將來事實相反.
條件句有真實條件句和非真實(虛擬)條件句兩種.真實條件句所表示的假設(shè)是有可能發(fā)生的,而非真實條件句則通常表示一種假想,與事實相反或不大可能會發(fā)生：
If I have time, I will go with them. 假若我有時間,我就同他們?nèi)?(陳述語氣)
If I were you, I would go with them. 假若我是你,我就同他們?nèi)?(虛擬語氣)
▲ 與現(xiàn)在事實相反
若與現(xiàn)在事實相反,條件從句的謂語用過去式(be通常用were),主句謂語用“should (would, could, might)+動詞原形”：
If I knew her number ,I could ring her up. 要是我知道她的電話號碼,我就可以給她打電話了.(可惜我不知道)
▲與過去事實相反
若與過去事實相反,條件從句的謂語用過去完成時(had+過去分詞),主句謂語用“should (would, could, might)+have+過去分詞”：
If I’d left sooner,I’d have been on time. 要是我早點動身,我就準(zhǔn)時到了.(但我動身太遲了)
▲與將來事實相反
若與將來事實相反,條件從句的謂語用過去式(be通常用were),主句謂語用“should (would, could, might)+動詞原形”：
If I asked him,I’m sure he’d help us. 如果我向他提出要求,肯定他會幫助我們.(不過我不打算這樣做)
注：幾點特別說明
① 主句謂語中的should主要用于第一人稱后.would, might, could的大致區(qū)別是：would表示結(jié)果,might表示可能性,could表示能力、允許或可能性.比較：
If you tried again ,you would succeed. 要是你再試一試,你就會成功的.(would表結(jié)果)
If you tried again, you might succeed. 要是你再試一試,你可能會成功的.(might表可能)
If you tried again ,you could succeed. 要是你再試一試,你就能成功了.(could表能力)
④ 對于與將來事實相反的情形,請注意以下幾點：一是這里說的與將來事實相反,實為對將來情況的推測；二是此用法中的條件從句謂語除用過去式外,有時也用“should+動詞原形”(表示可能性極小,常譯為“萬一”)或“were to+動詞原形”(表示與將來事實相反的假設(shè))；三是當(dāng)條件從句使用“should+動詞原形”這樣的謂語時,主句謂語除可用“should (would, could, might)+動詞原形”這樣的虛擬語氣外,也可用直陳語氣或祈使語氣：
If it should rain tomorrow, don’t expect me. 萬一明天下雨,就不要等我了.（祈使語氣）
If I should see him, I’ll tell him. 萬一我見到他,我就告訴他.（直陳語氣）
2、錯綜時間虛擬條件句
所謂錯綜時間虛擬條件句即條件從句與主句所指時間不一致,如從句指過去,而主句即指的是現(xiàn)在或?qū)?此時應(yīng)根據(jù)具體的語境情況,結(jié)合上面提到的三種基本類型對時態(tài)作相應(yīng)的調(diào)整：
If it had rained last night, the ground would be wet now. 要是昨晚下過雨的話,現(xiàn)在地面就會是濕的.
You would be much better now if you had taken my advice. 假若你當(dāng)時聽我的話,你現(xiàn)在就會好多了.
3、兩個常考虛擬語氣句型
▲ 句型介紹
這兩個句型是If it weren’t for…和If it hadn’t been for…,這是兩個很常用的虛擬語氣句型,也經(jīng)常受到命題人的青睞,其意為“若不是(有)”“要不是有”.如：
If it weren’t for water, no plant could grow. 要是沒有水植物就無法生長.
If it hadn’t been for your assistance ,we wouldn’t have succeeded.
=But for your assistance ,we wouldn’t have succeeded.
=Without your assistance ,we wouldn’t have succeeded.
5、wish后賓語從句用虛擬語氣
▲ 用法說明
動詞wish后接賓語從句時,從句謂語要用虛擬語氣.若要表示與現(xiàn)在事實相反的愿望,從句謂語用一般過去時或過去進(jìn)行時；若表示與過去相反的愿望,從句謂語用過去完成時或would / could+have +過去分詞；若表示將來沒有把握或不太可能實現(xiàn)的愿望,用would (could)＋動詞原形.如：
注：特別注意
從句的時態(tài)只與從句所指的時間有關(guān),而與wish的時態(tài)無關(guān),比較：
I wish I were rich. 要是我現(xiàn)在有錢就好了.
I wish I had been rich. 要是那時我有錢就好了.
I wished I were rich. 當(dāng)時我后悔自己沒有錢.
I wished I had been rich. 當(dāng)時我后悔自己曾經(jīng)沒有錢.
6、if only后的句子用虛擬語氣
if only 與 I wish一樣,也用于表示與事實相反的愿望,其后所虛擬語氣的時態(tài)與 wish后所接時態(tài)的情況相同：
If only she had had more courage! 她再勇敢一些就好了.
If only I had listened to my parents! 我要是當(dāng)時聽了父母的話就好了.
If only she would go with me! 她要是愿意和我一道去就好了!
注：if only 通常獨立使用,沒有主句.
7、as if (though) 從句用虛擬語氣
▲ 基本用法
以as if (as though)引導(dǎo)的方式狀語從句或表語從句,有時用虛擬語氣,若表示與現(xiàn)在事實相反,謂語動詞用一般過去時；若表示與過去事實相反,用過去完成時；表示將來的可能性不大,用would (might, could)+動詞原形：
He acts as if he knew me. 他顯得認(rèn)識我似的.
They treat me as though I were a stranger. 他們待我如陌生人.
He talks as if he had been abroad. 他說起話來好像曾經(jīng)出過國.
注：兩點說明
(1) 從句所表示的內(nèi)容若為事實或可能為事實,也可用陳述語氣：
It looks as if we’ll be late. 我們似乎要遲到了.
(2) 注意 It isn’t as if…的翻譯：
It isn’t as if he were poor. 他不像窮的樣子(或他又不窮).
8、It’s time后的從句用虛擬語氣
▲ 基本用法
從句謂語通常用過去式表示現(xiàn)在或?qū)?有時也用過去進(jìn)行時或“should+動詞原形”(較少見,且should不能省略),其意為“(早)該干某事了”：
It’s time we went [were going, should go]. 我們該走了.
It’s time I was in bed. 我該上床睡了.(不用were)
9、would rather后句子用虛擬語氣
在would rather, would sooner, would just as soon 后的that從句中, 句子謂語習(xí)慣上要用虛擬語氣, 表示”寧愿做什么” ,具體用法為：
▲ 一般過去時表示現(xiàn)在或?qū)淼脑竿?
I’d rather you went tomorrow (now). 我寧愿你明天(現(xiàn)在)去.
▲ 用過去完成時表過去的愿望
I’d rather you hadn’t said it. 我真希望你沒有這樣說過.
10、賓語從句用虛擬語氣的10種類型
▲ I wish后的賓語從句
動詞wish后接賓語從句時,從句謂語要用虛擬語氣.若要表示與現(xiàn)在事實相反的愿望,從句謂語用一般過去時或過去進(jìn)行時；若表示與過去相反的愿望,從句謂語用過去完成時或would / could+have +過去分詞；若表示將來沒有把握或不太可能實現(xiàn)的愿望,用would (could)＋動詞原形.如：
I wish I could be of some use. 我希望我能有什么用處.
We wish he didn’t smoke. 我們希望他不吸煙.
I wish prices would come down. 我希望物價能降下來.
▲ 表示“堅持”后的賓語從句
主要是指insist的賓語從句,從句謂語由“should+動詞原形”構(gòu)成,其中的should在美國英語中通常可以省略.如：
I insisted that he (should) stay. 我堅持要他留下.
注：動詞insist后接賓語從句時,除可用虛擬語氣外,也可用陳述語氣,兩者的區(qū)別是：若謂語動詞所表示的動作尚未發(fā)生,或尚未成為事實,則用虛擬語氣；若謂語動詞所表示的動作已經(jīng)發(fā)生,或已經(jīng)成為事實,則要用陳述語氣.比較：
He insisted that I had read his letter. 他堅持說我看過他的信.
He insisted that I should read his letter. 他堅持要我看他的信.
▲ 表示“命令”后的賓語從句
主要是指order, command的賓語從句,從句謂語由“should+動詞原形”構(gòu)成,其中的should在美國英語中通常可以省略.如：
He ordered that it (should) be sent back. 他命令把它送回去.
▲ 表示“建議”后的賓語從句
主要是指advise, suggest, propose, recommend等的賓語從句,從句謂語由“should+動詞原形”構(gòu)成,其中的should在美國英語中通?？梢允÷?如：
He suggested that we should leave early. 他建議我們早點動身.
注：與動詞insist相似,動詞suggest后接賓語從句時,除可用虛擬語氣外,也可用陳述語氣,兩者的區(qū)別也是：若謂語動詞所表示的情況尚未成為事實,則用虛擬語氣,此時suggest通常譯為“建議”；若謂語動詞所表示的情況為既成事實,則要用陳述語氣,此時的suggest通常譯為“表明”、“認(rèn)為”.比較并體會：
He suggested that we (should) stay for dinner. 他建議我們留下吃飯.
I suggested that you had a secret understanding with him. 我覺得你與他心照不宣.
▲ 表示“要求”后的賓語從句
主要是指ask, demand, require, request等后的賓語從句,從句謂語由“should+動詞原形”構(gòu)成,其中的should在美國英語中通?？梢允÷?如：
I ask that he leave. 我要求他走開.
He requires that I (should) appear. 他要求我出場.
▲ 表示“提議”“投票”后的賓語從句
主要是指move, vote等后的賓語從句,從句謂語由“should+動詞原形”構(gòu)成,其中的should在美國英語中通?？梢允÷?如：
I move that we accept the proposal. 我提議通過這項提案.
▲ 表示“敦促”后的賓語從句
主要是指動詞urge后的賓語從句,從句謂語由“should+動詞原形”構(gòu)成,其中的should在美國英語中通?？梢允÷?如：
He urged that they go to Europe. 他敦促他們到歐洲去.
▲ 表示“安排”后的賓語從句
主要是指動詞arrange后的賓語從句,從句謂語由“should+動詞原形”構(gòu)成,其中的should在美國英語中通?？梢允÷?如：
He arranged that I should go abroad. 他安排我去國外.
▲ 表示“希望”“打算”后的賓語從句
主要是指動詞desire, intend后的賓語從句,從句謂語由“should+動詞原形”構(gòu)成,其中的should在美國英語中通常可以省略.如：
She desires that he do it. 她希望他做此事.
▲ 表示“指示”后的賓語從句
主要是指動詞direct后的賓語從句,從句謂語由“should+動詞原形”構(gòu)成,其中的should在美國英語中通?？梢允÷?如：
The general directed that the prisoners should be set free. 將軍指示釋放那些俘虜.
11、主語從句中的虛擬語氣
在It is necessary,important,strange,natural, advisable, anxious, compulsory, crucial, desirable, eager, essential, fitting, imperative(絕對必要), impossible, improper, obligatory, possible, preferable, probable, recommended, urgent, vital etc. ；it is a pity；It is requested/suggested/desired/proposed等結(jié)構(gòu)后的主語從句中要用虛擬語氣,即Should+動詞原形或只用動詞原形.如：
▲ It’s important…類
這一類型主要包括It is (was) important (necessary, desirable, imperative, advisable)that. . .句型.如：
It is impossible that he should go home. 他不可能會回家去.
▲ It’s a pity…類
It is a pity that she should fare so badly. 她竟吃得這么差,真可憐.
▲ It’s desired…類
這種主語從句還常用在It is (was) desired (suggested, settled, proposed, requested, decided, etc. ) that...句型.如：
It is requested that a vote be taken. 建議付諸表決.
12、表語從句、同位語從句中的虛擬語氣
在advice, agreement, command, decision, decree, demand, determination, indication, insistence, order, preference, proposal, request, requirement, stipulation ,suggestion, idea,plan,order等名詞后的表語從句、同位語從句中要用虛擬語氣,即should+動詞原形或只用動詞原形.如：
Our suggestion is that you（ should）be the first to go． 我們的建議是你應(yīng)該第一個去.
13、 在 lest ,for fear that( 以免) , in case (以防)引導(dǎo)的目的狀語從句中的虛擬語氣
在 lest ,for fear that( 以免) , in case (以防)從句中用should＋動詞原形, should 可以省略.
She walked quietly lest she (should) wake up her roommates. 她走得很輕以免吵醒她的室友.
為方便記憶,表格對比
使用虛擬語氣的主要句型 謂語動詞的虛擬形式 例句
表現(xiàn)在的虛擬條件句 從句：用動詞過去（be 多用were ） 1. If I were you, I should study English.
2. I would certainly go if I had time.
主句：would/should/could/might+動詞原形
表過去的虛擬條件句 從句：had + PP 1. If you had taken my advice, you would not have failed in the test.
2. If I had left a little earlier, I would have caught the train.
主句：would/should/could/might +have + PP
表將來的虛擬條件句 從句：①用動詞過去②should +V原③（were +to do ） 1. If it were to rain tomorrow, the meeting would be put off.
2. If you came tomorrow, we would have the meeting.
主句：would/should/could/might +have + PP
省略 if 的條件句 從句：用倒裝形式,即把were,had等置于句首.(并只限were/ had)
主句：根據(jù)虛擬的情況采取與從句相應(yīng)的形式. 1. Were I in school again(= If I were in school again, I would work harder.)
2. Were it not for the rain, (不能說Weren’t it for the rain, ) I would go swimming.
錯綜時間條件句（從句與主句所表示時間不一致） 根據(jù)從句與主句表示的不同時進(jìn)行調(diào)整. 1.If you had worked hard yesterday, you would be tired now
2. If we hadn’t been working hard in the past few years, things woud be going so smoothly.
含蓄條件句（虛擬條件暗含在短語或上下文之中,從句不表現(xiàn)出來）(常見有but for“要不是” without等) 根據(jù)句子表達(dá)的實際情況選用相應(yīng)的虛擬條件句中的主句的動詞形式 1.Without air, there would be no living things.
2.I would have given you more help, but I was busy now.
名詞性從句中的虛擬語氣
wish, “可惜……”“……就好了”,“悔不該……”“但愿……” wish后從句：與表各種時間的虛擬條件句中的從句動詞形式基本相同.
具體：1,表與現(xiàn)在不能實現(xiàn)的愿望,從句用“過去時,be 用were”
2.表與過去不能實現(xiàn)的愿望,從句用“had+PP 或 could/would +have +PP“
3. .表與將來不能實現(xiàn)的愿望,從句用“could/would +動詞原形”
1.I wish I were a bird.
2. I wish I had known the answer..
would rather 后的賓語從句 would rather后從句：動詞常用過去式 1. I would rather they came tomorrow
demand, insist,suggest, command, order, require, request, desire等一類動詞后的賓語從句
（suggest表“暗示、隱含等”insist表“強調(diào),力言等”不用虛擬語氣.） 從句謂語用“should+動詞原形”,should可省. 1. I suggest you (should)go at once.
2. He suggested that he patient’s leg should be cut and this suggested that he was not good at the case.(注意兩個suggest的準(zhǔn)確翻譯)
“It is (was)+上述demand/suggest等動詞過去分詞（或important,natural,strange ,necessary等形容詞）”后的主語從句 從句謂語用“should+動詞原形”,should可省. 1. It ordered that the army (should) get there by 4 a.m.
2. It is necessary that she (should) be sent there at once.
order,suggestion,idea,plan, proposal, advice, demand等名詞后的表語從句或同位語從句 從句謂語用“should+動詞原形”,should可省. His demand is that we (should )finish the work in 3 hours.
特殊形式的虛擬語氣
as if 引導(dǎo)的從句（表示非真實時）但表真實時,不用虛擬語氣. 與虛擬語氣條件中從句動詞形式基本相同. 1.Tom speaks as if he were a girl.
2.He looks as if he had been to Beijing.
so that, in order that引導(dǎo)的目的狀語從句 May/might/should +V原 I live so that others may live better.
It is (the very/high)time that后的定語從句 從句謂語動詞常用過去式,有時也可用should+動詞原形 It is (high)time that we went (should go) to bed.
It is time that I were leaving.
省去主句的If only(要是……就好了)虛擬條件句 與wish后的賓語從句謂語形式相同. If only I hadn’t lost the chance!
(= I wish I hadn’t lost the chance)
某些表祝愿的句子 常用原形或“May+動詞原形” Long live world peace!
May you be happy1
表委婉客氣的是常語句 情態(tài)動詞的過去式+動詞原形 Could I borrow your bike?
Would you please give me a hand?
虛擬語氣的用法
虛擬語氣表示一種假設(shè)的情況,或一種主觀的愿望,即動詞所表示的動作或狀態(tài)并非事實,或不可能實現(xiàn).英語虛擬語氣的形式有下列幾種：
一、與現(xiàn)在事實相反
連接詞 條件從句 結(jié)果從句
If 1.動詞過去式(或were)
2.助動詞（過去式）+動詞原形 Should
Would +動詞原形
could
might
If had the time, John would make a trip to China to see the Great Wall.
If I were you, I would give up drinking immediately.
二.與將來事實相反
連接詞 條件從句 結(jié)果從句
If 1. should+動詞原形
2. 動詞過去式
3、were to+動詞原形 Should
Would +動詞原形
could r/>might
If you should lose, what would you do?
If I were to see her tomorrow, I would tell her thetruth.
If you went there next time, you would see what I mean.
三、與過去事實相反
連接詞 條件從句 結(jié)果從句
If had+過去分詞 Should
Would + have+過去分詞
could
might
If I’d dnown that it was going to rain, I would never have gone for a walk in the country.
四、虛擬語氣的幾種特殊用法
省掉if的條件從句結(jié)構(gòu)：
Had you asked me, I would have told you. (=If you had asked me,…)
2.有時虛擬條件不用條件從句而用不定式、分詞、介詞、名詞、連接詞或定語從句來表示,如：
A true friend would not do such a thing.
(=If he were a true friend, he...)
(=If there were no water,…)
(=If you hadn’t helped me,…)
3. 有時條件從句中的動作和結(jié)果從句中的動作發(fā)生的時間不一致,如：
If he had followed the doctor’s advice, he would be quite all right now.
If I were you, I would have gone home.
五、虛擬語氣的其他用法
1、Suggest, advise 等動詞之后賓語從句須用虛擬語氣,其句子結(jié)構(gòu)如下：
suggest, advise, recommend, demand,
require, insist, urge, request, order, +that…(should )+動詞原形
devide, ask, move, propose等
注意：在此結(jié)構(gòu)中that不可省略；should省不省均可.
He suggested that they (should ) stop smoking.
上述動詞的名詞形式出現(xiàn)時,that 引導(dǎo)的從句仍用虛擬語氣.
He made a request that they (should ) stop smoking.
如果that 引導(dǎo)的從句所表達(dá)的內(nèi)容是事實,也可用陳述語氣.
He insists that he is right.
2、It is (was )+necessary, a pity 等+that引導(dǎo)的從句須用虛擬語氣,其句子結(jié)構(gòu)如下：
imperative, advisable, 動詞完成式
It is (was) + important,natural, necessary, +that…(should) +
essential, strange,等 動詞原形
It is important that you (should) follow the doctor’s orders.
It is right that you should have done your homework.
3、wish的用法
動詞過去式或were—與現(xiàn)在事實相反
主語+wish(that)+主語 + 動詞過去完成式—與過去事實相反
助動詞過去試+動詞原形—與將來事實相反
I wish I were a pop singer. (=I am sorry I am not a pop singer..)
I wish I had never stopped teaching. (=I am sorry I stopped teaching.)
I wish they’d let us get some sleep.
注意：wish與hope接賓語從句的區(qū)別在于：hope表示一般可以實現(xiàn)的希望,賓語從句用陳述語氣.wish表示很難或不大可能實現(xiàn)的希望,賓語從句用虛擬語氣.試比較：
（1） We hope they will come,(We don’t know if they can come.)
（2） We wish they could come,(We know they are not coming.)
4、as if, as though, would(had) rather(that)引導(dǎo)的從句須用虛擬語氣,如：
He acts as if nothing had happened.
I would rather you didn’t tell him.
5、It’s (high) time that…+動詞過去式或should+動詞原形,如：
It’s time (that) you had a hair cut.
It’s high time (that) we took some action.