1、四六級考試常考英語語法一 定語從句引導定語從句的有關系代詞as，who，whom，whom，which，that和關系副詞when，where，why等。1.as引導定語從句（1）as引導定語從句，相當于which。如I am from shanghai，as/which you know。但as引導的定語從句可以放在句首，而which不能；例：As you know，I am from shanghai。（2）as可作為關系代詞來引導定語從句，既可以單獨引導從句，又可以與主句中的the same 或such 相呼應，從句中的謂語動詞常省略。2.關系代詞that與which用法區別：（1）wh

2、ich可以引導一個非限制性定語從句，that則不能；（2）which之前可以有介詞，that之前則不能；（3）只能用that，而不能用which的主要情形：當先行詞是all，anything，few，little，much，none，nothing，something等不定代詞時；當先行詞被序數詞或形容詞最高級修飾時；當先行詞被the very，the only等詞修飾時。例：Medical researchers are painfully aware that there are many problems to which they have not found solutions so

3、 far。二 狀語從句1. 讓步狀語從句（1） 由no matter + wh-疑問詞【no matter what】 和wh-疑問詞+ever【whatever】。但wh-疑問詞+ever【whatever】引導的名詞從句則不能用no matter替換。Take the coat ，no matter what coat it is / whatever coat it is .（2） No matter whetheror結構中可將no matter省略，形成whetheror或whetheror not 引導選擇條件句。例；The substance does not dissolve

4、in water whether it isheated or not。2條件狀語從句翻譯條件狀語從句時，要注意時態的選擇。例；Please come here at ten tomorrow morning if it is convenient for you。條件狀語從句，用if引導；主句是祈使句，相當于將來時態，故從句應用一般現在時。3. 時間狀語從句例；We do not know it until a doctor discovered it by chance。4. 原因狀語從句常見引導原因狀語從句的引導詞有；because，as，now that/since， in that等

5、。三 名詞性從句 1. 主語從句漢語中的“的”字結構可譯成英語的主語從句，用what引導，相當于the thing that。例：What many people have not realized is that read books is a insteresting thing。2. 表語從句In my seventies，one change I notice is that I am more easily to get tired than before。四 比較結構1. asas【與一樣】，morethan【比更】，a bit/a little/a lot/even/far/gr

6、etly/many/much/sightly/still+形容詞/副詞比較級這些結構。注意：more than 表示不只是，只不過；no morethan=notany more than,表示與一樣不。例：I would prefer shopping online to shopping in a department store because it is more convenient and time-saving。例：Since my childhood I have found that nothing is more attractive to me than reading。

7、2The morethe more“越越”例：The more you explain ，the more confused me。3倍數表達法A is 倍數+the size/length/width of B【A是B的幾倍大/長/寬】A is 倍數+形容詞或副詞原級+as B【A是B的幾倍】A is 倍數 more than B【A是B的幾倍】例：On average，it is said,visitors spend only half as much money in a day in Leeds as in London. 4.表示與相比較的短語compare with和in com

8、parison with例：Your losses in trade this year are nothing compared with/in comparison with mine。五 情態動詞1. 情態動詞中的must，can，could，may，might都表示推測。其中must可能性最大，can和could其次，may和might最小。2. 情態動詞完成時所表達的意義：could have done 本科可能做may/might have done 也許做了should have done 本應做must have done 肯定做過六 倒裝結構1. 有否定含義的副詞或短語位于句

9、首作狀語，這類詞有：neither，never，no，rarely，hardlywhen，little，few，in no case ，no soonerthan等。例：Not until he fanish his work did he realize he was seriously ill。2. 含有only的狀語或賓語位于句首時，其句子的主謂要部分倒裝。例：Not only did he charge me too much，but he completed his mission。3虛擬語氣的讓步狀語從句中，在省略了lf的情況下主謂部分倒裝。Had I taken your adv

10、ice【if I had taken your advice 】，all this misery might have been avoided。七 虛擬語氣1. 虛擬語氣用于非真實條件句（1）由if引導的非真實條件句表示對現在過去將來的事實進行假設時，主從，句的謂語動詞形式如下所示表虛擬的時間If從句謂語形式主句謂語形式現在過去時Would/should/could/might+動詞原形過去Had+過去分詞Would/should/could/might+have done將來一般過去時 Were to+動詞原形Should+動詞原形Would/should/could/might+動詞原形

11、例：If she had returned an hour latter，Mary would not have been caught in the heave rain。（2）有些介詞或介詞短語含有隱含的條件含義，其虛擬形式與if引導的非真實條件狀語從句類似，需根據從句所用的時態，來選擇主句謂語形式。這些詞包括：without，but for，were it not for等。2.虛擬語氣用于狀語（1）lest，in case 或 for fear that 引導的目的狀語從句中，謂語動詞用【should+動詞原形】（2）在as if或as though引導的方式狀語從句中，謂語動詞虛擬式

12、的變化要依據對過去，現在，將來的假設選擇適當的動詞虛擬式。例：You would better take a sweater with you in case it gets cold。3.虛擬語氣用于賓語從句中（1） Wish后的賓語從句可用三種謂語動詞形式表示虛擬：一般過去時表示對現在情況的假設過去完成時表示對過去情況的假設would+動詞原形表示對將來的愿望例：sometimes I wish I were living in a different time and different place。（2） would rather，would sooner，might as well，

13、would prefer 后面跟虛擬語氣表示愿望，意為寧愿，但愿，形式為：would ranther/sooner+主語+謂語動詞過去式 表示現在或將來的愿望would ranther/sooner+主語+動詞過去完成時 表示過去的愿望例：I would rather I had not gone to the party yesterday。（3） if only引導的感嘆句表示但愿，要是就好了。其用法和wish基本相同，只是感情色彩更強烈。（4） 在表示命令，建議等動詞后的賓語從句中要求用虛擬語氣形式，謂語形式為should+動詞原形例：The teacher raquired that we should hand in our homework by Wednesday。4.it is +形容詞/名詞+that結構中例：