一、非真實(shí)條件句中的虛擬語氣
　　1.和現(xiàn)在的事實(shí)相反
　　從句：一般過去時(shí)（were/done）；主句：過去將來時(shí)（would do）
　　E.g.：I am not free today. If I ___ free today, I __ and visit some of my friends.
　　2.和過去的事實(shí)相反
　　從句：過去完成時(shí)（had done）；主句：過去完成時(shí)（would have done）
　　E.g.：If my lawyer ___ here last Saturday, he __ me from going.
　　3.和將來的事實(shí)相反
　　從句：①were to + 動詞原形 ②should+動詞原形 ③動詞過去式；
　　主句should/would/could/might+動詞原形
　　E.g.：If I were to see Tom, what ___ you ___ me to tell him?
　　二、賓語從句中的虛擬語氣
　　1.wish后面賓語從句中的虛擬語氣，表示與事實(shí)相反的愿望。其表達(dá)形式一般是將從句的謂語動詞退后一個(gè)時(shí)態(tài)。例如:
　　1)與現(xiàn)在事實(shí)相反: wish + (that)+ did(were)
　　E.g.：I wish I were as healthy as you.
　　E.g.：I wish that I had a plane.
　　2)與過去事實(shí)相反 : wish + (that)+ had done
　　E.g.：I wish I had been to the concert last night.
　　E.g.：I wish you had written to him.
　　3)與將來事實(shí)相反 : wish + would/could/might + do
　　E.g.：I wish he would forgive me.
　　2. 在某些動詞后的賓語從句中需用should+動詞原形的虛擬語氣形式?！皊hould”可以省略。
　　一個(gè)堅(jiān)持insist; 兩個(gè)命令order,command ; 三條建議suggest , advise, propose;
　　四項(xiàng)要求demand, request,require, ask; 另外有:prefer、recommend
　　注意: suggest表“暗示表明”時(shí) insist表“堅(jiān)持認(rèn)為”時(shí)不用虛擬語氣
　　E.g.：He ordered that the students (should) wash the clothes every week by themselves.
　　E.g.：The doctor suggested that she (should) have an operation at once.
　　*His face suggested that he had been punished by the teacher.
　　三、主語從句中的虛擬語氣
　　1.  Itbe+過去分詞+that…+(should)+動詞原形+…
　　過去分詞：suggested, requested, ordered,proposed
　　E.g.: It is required that nobody (should) smoke here.
　　E.g.: It's suggested that everybody (should) buy a dictionary
　　2. It be+形容詞+that…+(should)+動詞原形+…
　　形容詞:important, necessary, natural,right, wrong, better, proper, funny, strange, surprising…
　　E.g.: It is necessary that we(should ) have a walk now.
　　E.g.: It's important that we(should) take good care of the patient.
　　3. It be+名詞（ a pity/a shame/ no wonder） that…+ (should)+動詞原形+…(表示驚異、懊悔、失望等情感)
　　It is a regret that he (should)miss this golden chance.
　　四、表語從句、同位語從句中的虛擬語氣
　　在 suggestion, proposal, idea, plan, order, advice,decision等名詞后面的表語從句、同位語從句中要用虛擬語氣，即（should）+動詞原形。
　　E.g.: My suggestion is that we(should) leave at once.
　　E.g.: I make a proposal that we(should) hold a meeting next week.
　　五、狀語從句中的虛擬語氣
　　1、用在由as if, as though引導(dǎo)的狀語從句中，表示和現(xiàn)在事實(shí)相反或?qū)ΜF(xiàn)在的懷疑，用過去時(shí)；表示過去想象中的動作或情況，用過去完成時(shí);表示將來用would + 動詞原形。
　　E.g.: It seems as if the man were his brother.
　　E.g.: This device operated as though it had been repaired.
　　2.用在lest,for fear that和in case引導(dǎo)的狀語從句中，這時(shí)謂語動詞用(should)+動詞原形
　　E.g.: She closed the windows lest she catch cold.
　　六、其他句式
　　1、It's(high/low) time 從句：
　　It is (high) time that從句謂語動詞要用過去式或用should加動詞原形，但should不可省略。
　　E.g.: It is time that the children went to bed.
　　E.g.: It is high time that the children should go to bed.
　　2、一些介詞短語
　　But for your help, we couldn't have succeeded.
　　Nothing could live without the sun.
　　3、比較if only與only if
　　only if 表示“只有”；
　　I wake up only if the alarm clock rings.
　　if only 則表示“如果……就好了”。其從句中的謂語動詞用過去時(shí)或過去完成時(shí)。
　　If only I knew more.
　　If only the alarm clock had rung.
　　七、虛擬語氣難點(diǎn)
　　1、錯(cuò)綜虛擬與隱含虛擬
　　錯(cuò)綜虛擬：If you hadn't bought the ticket last week, how would you go now?
　　隱含虛擬：情境中提供虛擬語氣
　　Suppose there were no gravity,objects would not fall to the ground when dropped.
　　She wasn't feeling very well.Otherwise she wouldn't have left the meeting so early.
　　He telephoned to inform me of your birthday, or I would have known nothing about it .（連詞）
　　I might have given you more help, but I was too busy .（連詞）
　　Given more time, we could have done it better .（分詞短語）
　　… … Such mistakes could have been avoided .（通過上下文）
　　2、倒裝
　?、?Were it (=If it were) not for their help, we couldn't have got over the difficulties.
　?、?Had I (=If I had) known about it, I would have told you.
　　③ Should anyone (=If anyone should) call, please take a message.