初中英语知识点总结

　　I.要点

　　表示说的话不是事实，或者是不可能发生的情况，而是一种愿望、建议或与事实相反的假设等。一般常用于正式的书面语中。

　　1、虚拟语气的构成

　　如：与现在事实相反

　　If I had more time, I should study German.(fact:I have no more time, so I shall not study German. )

　　If she were not so busy, she would attend the meeting this afternoon.(fact:she is very busy, so she will not attend the meeting this afternoon.)

　　If they didn’t take physical exercises every day, they wouldn’t be so healthy.(fact: they take physical exercises every day, so they are very healthy.)

　　与过去事实相反：

　　I would have checked my paper again if I had had more time at yesterday’s examination.(fact:I had no more time at yesterday’s exam, so I didn’t check my paper again)

　　You would have already recovered from his illness if he had seen the doctor in good time.(fact: He didn’t see the doctor in good time ,so he hasn’t recovered from his illness )

　　与将来事实相反：

　　If it rains tomorrow, our picnic will be put off.(The weather has been changeable these days.)

　　If it rained tomorrow, our picnic would be put off.( The weather has beenvery good these days.)

　　If it should rain tomorrow, our picnic would be put off.(That would be out of our expectation.)

　　If it were to rain tomorrow, our picnic would be put off. (条件从句谓语动词用were to +动词原形，表示下雨的可能性极小。Were to rain和should rain都表示“出乎意料之外”，但were to加强表示“当初没想到以后的事”)

　　注：

　　(1)如果条件从句谓语动词包含有were或had, should, could有时可将if省去,但要倒装。如：

　　Had you (If you had) invited us, we would have come to your party.

　　(2)混合时间条件句的用法：

　　有时条件从句的动作和主句动作发生的时间不一致。这时动词的形式，应根据它所要表达的具体时间来决定用什么形式。

　　1) If she hadn’t trained so hard, she wouldn’t be run so fast.(从句叙述过去，主句叙述现在。)

　　(fact: she has trained very hard, so she would able to run fast.)

　　2)You would speak English well enough if you had practised reading and speaking it every day.(主句叙述现在，从句叙述过去)

　　(fact: You didn’t practice (hasn’t practiced ) reading and speaking it every day, so you can’t speak English well enough.)

　　(3)在其他状语从句中的.用法

　　主要用于由as if (as though)引导的比较状语从句，从句中谓语动词一般用“动词的过去式(be变were )或had +过去分词。”如：

　　She looked as if she were ill.(实际上她没有病，在这里用虚拟语气补语比喻她精神不佳)

　　Xiao Liu speaks English so well as if he had studied in England.(这里用虚拟语气表现他的英语说得好)

　　2、虚拟语气在各种从句的应用

　　(1)在主语从句中用来表示惊奇、惋惜、理应如此等，其谓语形式是"should(可省) +动词原形"，常用于以下三种句型中。

　　句型一：It is necessary (important, natural, strange, etc) that…

　　句型二：It is a pity (a shame, no wonder, etc) that…

　　句型三：It is suggested (requested, proposed, desired, etc) that…

　　如：It is strange that he (should) have done that.

　　It is a pity that he (should) be so careless.

　　It is requested that we (should) be so careless.

　　(2)在宾语从句中用于suggest, propose, move, insist, desire, demand, request, order, command等动词后的宾语从句中，表间接的命令和建议。其谓语形式是"(should)+动词原形"。如：

　　I suggest that we (should) go swimming.

　　(3)在表语从句中，表示间接的命令，要求、请求、建议、决定等，主句中的主语通常是suggestion, proposal, request, orders, idea等。从句谓语形式是"(should)+动词原形"。如：

　　His suggestion is that we (should) leave at once.

　　(4)在同位语从句中，谓语形式是"(should)+动词原形"。如：

　　We received order that the work be done at once.

　　(5)在It is time that…句型中，其谓语动词形式是"动词的过去式"或"should +动词原形",should不可省。如：

　　It's time (that) we went ( should go) to school.