请问英语语法中的关联词的具体用法有谁知道？谢谢

　　关联词是历年高考所关注的热点，尤其那些既有区别又有联系的连词更是倍受命题者所青睐

　　一、that,what

　　1.两者都可引导名词性从句。

　　1)that本身无词义，常引导名词性从句，此时的从句意义已完整，常不省略(宾语从句除外)。

　　　　It worried her a bit that her hair was turning gray.(it为形式主语)

　　2)what引导名词性从句时，在从句中常作主语或宾语。如：

　　2.what一般不可引导定语从句，不能用作强调词；而that既可引导定语从句(由其前的先行词确定)，又可作强调词。如：

　　All that is needed is a supply of rice.

　　It was only when I reread the article lastnight that I realized the extended meaning.

　　3.what可作为感叹词引导感叹句，而that不可。如：

　　What a long way it is from Beijing to Lon-don!

　　二、whether ,if

　　1.两者都能引导名词性从句之异同：

　　1)当引导一个没有疑问词的问句时，两者均可。如：

　　I'm not sure whether(if)I'll have time.

　　2)当提出两种选择时要用whether。如：

　　Let me know whether you can come or not.

　　3)whether可用在介词后，if则不可。如：

　　I haven't settled the question of whether I'll go back home.

　　4)whether可与不定式连用，if则不行。如：

　　She doesn't know whether to get married now or wait.

　　5)引导主语从句时，if不能放句首，whether在句首、句中均可。如：

　　　It is doubtful if(whether)he is coming.

　　2.if还可以引起条件状语从句，whether不可以。如：

　　If we try hard,we'll be able to complete the task in time.

　　3.whether...or(无论)，引起让步状语从句，if不可。如：

　　Whether you come or not,I'll set off on time.

　　三、in case，if

　　两者都引导条件状语从句。

　　1)in case作"如果"意义时，常放在句前，可与if替换。如：

　　In case(If)he comes,let me know.

　　2)in case作"免得，以防"意义时常放在主句后，不能用if替换。试比较：

　　You should insure your house in case there's a fire.

　　John may call tonight.I don't want to go out in case he phones.

　　I don't think I'll need any small change but I'll bring some in case.

　　You should call 999if there's a fire.

　　四、though,although,as

　　这三个词都有转折之意，表示"虽然"、"尽管"。

　　1.though和although引导让步状语从句时，常可互换，只是although的语气较强些，其主句前可用副词yet,still,nevertheless修饰，也可不用。如：

　　Though／Although it was late,the farmer kept on harvesting the crops by the lights of the tractors.

　　Though he was old,(yet)he worked hard.

　　2.though作连词时，可以用于省略句，引起让步状语从句可以用部分倒装语序；作副词时表"可是"、"然而"，常放于句末，但上述用法不适用于although。如：

　　I've a bit of cold.It's nothing serious,though.

　　3.as引导让步状语从句时，从句用倒装语序，将表语、状语等置于句首，可与though互换。

　　Poor though /as I am，I can afford it.

　　五、however /whatever...,no matter how/what...

　　1.no matter what /how等只能引导以形容词或副词为中心的让步状语从句，且用部分倒装形式。如：

　　However /No matter how hard it may be，I must try.

　　2.however无论怎样，whatever无论什么，既可引导让步状语从句也可引导名词性从句，要视具体情况而定。如：

　　These wild flowers are so special that I would do whatever I can to save them.

　　However late he is,Mother will wait for him to have dinner together.

　　We will have to finish the job,however long it takes.

　　六、even if,even though

　　"即使"、"纵使"都可引导让步状语从句，但even if更强调假定性。如：

　　Even if he is poor,she loves him.＝He may be poor,yet she loves him.

　　Even though he is poor,she loves him.＝He is poor,yet she loves him.

　　Even though /if I didn't know anybody,Ihad a good time.

　　七、when,while

　　二者都可以引导时间状语从句，当从句的动词是延续性动词时，两者可互换。如：

　　He entered the room while(when)his mother was talking with his headteacher.

　　1.若要表示转折的对比，用while，意为"而，然而"。如：

　　She thought I was talking about her uncle,while in fact,I was talking about my uncle.

　　2.when相当于"and then"或"at the time that"也是常见考点，主句为特定时间，常用过去进行时或be about to do(即将发生)表达，从句表达的多是偶然性的动作。

　　八、unless(除非，如果不)，if...not

　　两者都引导条件状语从句。如：

　　He is sure to come unless he has some urgent business.

　　＝He is sure to come if he hasn't any urgent business.

　　The men will have to wait all day unless the doctor works faster.

　　1.当从句是虚拟形式时，只用if...not,不用unless引导。如：

　　The flowers would have died,if you had not watered diligently.

　　2.当主句为疑问句时，不用unless,而用if...not。如：

　　What shall we do if he doesn't reply to our letter?

　　3.当unless引导的从句带有否定词时，不能用if...not代替。如：

　　I'll go unless no one else goes.

　　九、till,until(直到……，直到……才)

　　1.都可引导时间状语从句，当从句在主句后面时，二者均可用；主句谓语动词为延续性动词，用肯定式；若是短暂性动词，用否定式。如：

　　Sandy had left his keys in the office so he had to wait until /till his wife came back.

　　They watched the train until /till it disappeared in the distance.

　　I didn't leave until /till he came back.

　　2.但是在句首或强调句中时，一般用until而不用till；在句首时，主句谓语要部分倒装而从句不倒装。如：

　　Not until all the fish died in the river did the farmers realize how serious the pollution was!

　　十、in order that,so that,so...that

　　1.前两者都可以引导目的状语从句，从句中通常要有can /could,m ay /might,will /would等情态动词，而且，当从句的主语与主句的主语一致时从句可转化为in order to do sth.／so as to do sth.／to do sth.。如：

　　John shut everybody out of the kitchen so that he could prepare his grand surprise for the party.

　　They set off for the station very early in order that /so that they might not miss the first bus.

　　They set off for the station very early in order not to miss the first bus.

　　2.后两者都可以引导结果状语从句，此时从句中一般不能用can /could,may /might,will /would等。如：

　　He got up very early so that he caught the first train.

　　The research is so designed that once begun nothing can be done to change it.

　　So difficult did I feel it to live in an English-speaking country that I determined to learn English well.

　　I devoted all my time to my studies so that I got good marks in all my subjects.

　　I felt so nervous that I shook like a leaf.

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