語氣是用來表示說話者的意圖和態(tài)度,。

         盡管英語中有陳述語氣（indicative mood）,、祈使語氣（imperative mood）、虛擬語氣(subjunctive mood)等,，但是在我國中高級英語考試中考的最多的是虛擬語氣,。

         虛擬語氣在英語里主要用來表達： 
　　      a. 非真實的情景,，不可能發(fā)生的事，即某種與事實相反或難以實現(xiàn)的情況,，或說話人主觀愿望,。 
　　      b. 與客觀事實相反的情景， 即強制性虛擬語氣,，表示建議,、命令、勸告等意思,，表示強烈地要求做到,、必須做到這樣的含義。 
　　

         虛擬語氣的表達形式是通過動詞的變化形式表達的,， 其特點是主從句時態(tài)的不一致,， 而且一般有明顯的標志,。具體考點如下：
 
　　考點一：

         if 句型 （共有三種句型） 
　　   1. 與現(xiàn)在的事實相反 
　　      從句用一般過去時,，主句的謂語用would (could, might) ＋動詞原形 
　　      If I were Bill Gates, I would not work so hard every day. 
　　

           2. 與過去的事實相反 
　　      從句用過去完成時，主句的謂語用would (could, might) ＋ 現(xiàn)在完成時 
　　      If I had gone to America when I graduated from middle school, I would have got my PhD degree. 
　　

           3. 與將來的事實相反 
　　      從句用should (were to,，did) + 動詞原形,，主句的謂語用would (could, might) ＋動詞原形 
　　      If it should / were to snow tomorrow, I would go skiing. 
　　

           4. 虛擬語氣條件句中if的省略，此時主謂要倒裝,。 
　　      Had he worked harder, he would have got through the exam. 
　　

           5. 條件句發(fā)生的動作和主句發(fā)生的動作不一致,，（例如：條件句動作發(fā)生在過去，主句的動作發(fā)生在現(xiàn)在）謂語動詞要根據(jù)表示的時間進行調(diào)整,。 
　　      If you had taken the medicine yesterday, you would feel much better now. 
　　      If I were you, I wouldn’t have missed the film last night. 

　　考點二：

         wish 句型 表達“但愿…,，要是…多好”的語氣 
　　 wish后賓語從句用虛擬語氣，其謂語部分有時態(tài)變化：

               表示對現(xiàn)在情況珠虛擬時,，動詞用一般過去時（如did）,；

               對過去的情況進行虛擬時，動詞用“過去完成時（如had done）或情態(tài)動詞的過去時 + 動詞的現(xiàn)在完成時（如could have done）”形式,；

               表示情況的虛擬時,，用“情態(tài)動詞的過去時形式 + 動詞原形（如might do）。” 
　　         I wish I had been to the concert last night. 
　　         I wish he would forgive me. 
　　         I wish I would remember all the English words in a week. 

　　同例： 在as if / as though引導(dǎo)的狀語從句中和以 if only引起的感嘆句中,，謂語動詞與wish引導(dǎo)的賓語從句中的虛擬形式相同,。例： 
　　      He talked as if he had known Tom for a long time. 
　　      He talks as if he were the boss. 他說起話來就像他是老板。  
             If only I were free now. （注意：if only…后面可以不加主句 ） 

　　考點三：

         在強制性語氣的賓語從句中,， 即表示建議,、命令、勸告,、決心等主觀色彩的動詞 + that + (should) + 動詞原形,， 其中should 經(jīng)常被省略,。這類動詞包括： 
　　   suggest, propose, recommend, demand, order, command, desire, require, insist, advise, decree (發(fā)布命令；下令), determine, prefer, stipulate, move（動議,，規(guī)定）,，direct（命令），maintain（堅持）,，decide,，ask 
　　   I suggest that you (should) not be late again next time. 
　　   I prefer that you (should) not do that. 我認為你還是別干那件事的好。 
　　

         注意一： 以上動詞的名詞（如：suggestion, proposal, demand, order, command, advice, desire, requirement, request, agreement, determination, preference , resolution, indication 等）后接同位語從句或表語從句時,，從句要求用虛擬語氣,，其謂語部分用“（should）+ 動詞原形” (should可省略)。 
　　   We are all for your proposal that the discussion be put off.     
　　   His demand is that all of us (should) be present at the meeting. 

      　注意二：以上這類動詞中有的動詞有時不表示建議,、命令,、勸告等，則其賓語從句不用虛擬語氣,。 
　　    What he said suggested（表明）that he did not agree with us. 

　　考點四：

         It is / was + 形容詞/過去分詞 + that + (should) + 動詞原形,，這些形容詞主要表示必要性、重要性,、強制性,、合適性、義務(wù)性,，即某人對某事的反應(yīng),。

         這類形容詞包括： 
　　   important, natural, desirable, possible, astonishing, advisable（可取的, 明智的）, anxious, appropriate, compulsory（義務(wù)的；強制的,；強迫的）, crucial (至關(guān)緊要的), eager, essential, fitting, imperative (命令的, 強制的, 必要的), improper, natural, necessary, obligatory (義不容辭的, 必須的), preferable, proper, urgent, vital, willing shocked, requested     
　　   It was essential that the application forms be sent back before the deadline. 
　　   It is requested that a vote be taken. 有人提請投票表決,。  
          It is necessary that we all should do our best to protect environment around us. 
　　注意：表示不可思議、滑稽,、不可想象,、令人吃驚等形容詞如amazing, strange, odd, ridiculous, surprising, unthinkable，incredible等后的that從句中should一般不省略,，翻譯為“竟然”,，表示說話人的驚異、懊悔,、失望等情感,。
 
　　 考點五：

         在 would rather…, would sooner…, had rather…, would just as soon…, would prefer… 意為“寧可，但愿”,。

         從句用虛擬語氣,，若

         It is surprising that they should pass the time like that. 
　　 It is incredible that Jane should have finished her paper so soon.     
　　 It is strange that there should be any hope of finding the lost child.

         表示現(xiàn)在或?qū)淼氖虑椋^語用過去時,；若表示過去的動作,，用過去完成時,。
　　 I would rather that you painted the room green.
　　 I’d just as soon you had returned the book yesterday.

　　考點六：

         It’s (about / high / good) time that…，表示“該是,。,。。的時候了”, 含有“晚一點” 的意思, 表示建議現(xiàn)在應(yīng)該做什么事,，從句通常用一般過去時,。
　　   It’s time you went to bed.    
　　   It’s high time that we took action.

　　考點七：

         在lest that …, for fear that…, in case that … 引導(dǎo)的表示消極意義的目的主語從句中常用虛擬語氣，表示“唯恐,，以免”,，從句用 should +動詞原形。
　　    He put his coat over the child for fear (lest) that he should catch cold.
　　    He emphasized it again and again lest she (should) forget.
　　比較：    
　　Take a hat with you in case the sun is very hot （該句陳述某一事實）

　　考點八：

         含蓄虛擬條件句    
　　   含蓄虛擬條件句是指沒有出現(xiàn)由if引導(dǎo)的條件句,，而條件句的意思是用其他方式來表達,。

          如：without, but for, otherwise, or, but that, given, provided, supposing, were it not for等。
　　      Without your help, we couldn’t have finished the work on time.     　
　　      But for the English examination I would have gone to the concert last night.
　　      I wouldn‘t have succeeded without your help.
　　      We didn’t know his telephone number; otherwise we would have telephoned him.