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1、2012届高考英语一轮复习语法系列课件：连词介词,连词 某些用法比较特殊的从属连词用法区别： 一、while, when, as引导时间状语从句时的区别 1while引导的状语从句中动词必须是持续性。谓语动词多为进行时，或状态动词的一般时。while的这些用法可用when代替，等于“at the time that”，“during the time that”。 例如：Please keep quiet while (when) others are studying. 2when除可指一段时间外，还可用来指一点时间，等于“at the time”，也就是说when引出的时间状语从句中的谓语
2、动词可以是终止性的，也可以延续性的。因此主句和从句的谓语可以是一般时，进行时，或完成时。 例如：When I went into the lab, the teacher was doing an experiment.(when不能换成while)He often makes mistakes when he is speaking English.(when可换成while),3as常可与when，while通用，但强调“一边、一边”。 例如：As (when, while) I was walking down the street, I noticed a police car in
3、front of number 37. 4when引导的状语从句中的主语与主句主语一致，主、谓是“主语系动词”结构时，这时主语和系动词可以省略。 例如：When (he was) young, he worked for a rich man./ Shell be here to give you help when (if it is) necessary. 5when有时代替if，引导条件句，意为“如果”、“假如”。 例如：Ill come when (if) Im free.,二、because, since, as引导原因状语时注意使用上的区别 1如果原因构成句子的最主要部分，一般用b
4、ecause ，因此because引导的从句往往放在句末。用why提问的句子，一定要用because回答。 例如：He had to stay at home yesterday because he was ill. 2如原因已为人们所知，或不如句子的其他部分重要，就用as，或 since。since比as更正式些。as和since引导的从句一般放在句子的开头。 例如：As you are tired, you had better rest./ Since everyone is here, now lets begin.,三、although和though引导让步状语从句往往用法一样，但
5、注意以下区别 1although用于各种文体，而though则多用于非正式的口语或书面语中。注意由although, though引导的从句后，主句不能用but，但可用副词yet, still。 例如：Although/ Though it rained all the morning, they still went on working.(或yet they went on working) 2though常与even连用，even though表示强调，意为“即使”，但不能说even although。 例如：Even though I didnt understand a word,
6、I kept smiling. 3though可用作副词，意为“然而”，常用逗号与句子分开。although则不能这样使用，它只作连词。 例如：It was a quiet party, I had a good time, though.,四、once作副词译“曾经”，作为连词译“一旦”，引导条件状语从句。相当于if的加强形式 例如：I dont believe he was once a thief. (once这里是副词)/ Once Aristotle had made up his mind that heavy objects always fell faster than lig
7、ht objects, he taught it as a truth to his students. (once连词) 五、unless引导条件状语从句等于if.not. 例如：Hell accept the job unless the salary is too low. ( Hell accept the job if the salary is not too low.) 六、在用as if引导的方式状语从句及表语从句中，根据情况要使用虚拟语气 例如：He talks as if he knew all about it. 但有时也可用直陈语气。例如：It looks as if
8、it is going to rain.,七、as作从属连词可引导多种状语从句 1as引导时间状语从句，意为“当时”。例如：As (he was) a young man, he was a storekeeper and later a postmaster./ He sang as he worked. 2as引导方式状语从句，意为“象一样”。例如：We must do as the Party teaches us. 3as引导原因状语从句。意为“由于”，例如：As you are tired, you had better rest. 4as引导让步状语从句。意为“虽然”、“尽管”。例
9、如：Child as he is, he can do it well. ( Although he is a child, he can do it well.) 另外，as作为关系代词还可以引导定语从句，如：I have the same book as you have.,介词 一、表示时间的at, in, on 1at表示片刻的时间，如：at 8 oclock，常用词组有：at noon, at night, at midnight, at the end of, at that time, at the beginning of, at the age of, at Christma
10、s, at New Year等。 2in表示一段的时间，如：in the morning, in the afternoon, in the evening, in October, in 1998, in summer, in the past, in the future等。 3on总是跟日子有关，on Monday, on Christmas morning, on the following, on May Day, on a warm morning等。,二、表示时间的since和from 1since表示从过去到现在的一段时间的过程，常与现在完成时连用。 2from表示从时间的某一
11、点开始，不涉及与现在的关系。一般多与现在时、过去时、将来时连用。如：I hope to do morning exercises from today./ We have not seen each other since 1995. 三、表示时间的in和after 两者都表示“在(某个时间)之后，区别在于in表示“在(一段时间)之后”，而after则表示“在(某一具体时间点之后)”，in短语和将来时态连用，after短语和过去时态或将来时态连用。如：Well be back in three days./ After seven the rain began to fall./ What s
12、hall we do after graduation? 注意：after有时也可以表示在一段时间之后(常用在过去时里)。如：After two months he returned.,四、表示地理位置的in, on, to in表示在某范围内，on指与什么毗邻，to指在某环境范围之外。如：Changchun is in the northeast of China./ Mongolia is on the north of China./ Japan is to the east of China. 五、表示“在上”的on和in on只表示在某物的表面上，而in表示占去某物一部分。如：The
13、re is a book on the piece of paper./ There is an interesting article in the newspaper./ He dug a hole in the wall. 六、表示“穿过”的through和across through表示从内部通过，与in有关；across则表示从一端至另一端在表面上的通过，与on有关。如： Water flows through the pipe./ The old man walked across the street.,七、in the corner, on the corner, at the
14、 corner in the corner表示在角落里，in指角的内面；on the corner表示“在角上”，on指的不是内面，也不是外面，而含内外兼有之意；at the corner指“在拐角处”，at指的是拐角外附近的外面。如：The lamp stands in the corner of the room./ I met with him at the street corner./ He sat on the corner of the table. 八、in the end, at the end of, by the end of in the end作“最后”、“终于”解，
15、可单独使用，后不接介词of；at the end of表示“在末梢”，“到尽头”，既可指时间，也可以指地上或物体。不可单独使用；by the end of作“在结束时”，“到末为止”解，只能指时间。不可单独使用。如：In the end they reached a place of safety./ At the end of the road stands a beautiful garden./ They decided to have an English evening at the end of this week./By the end of last month he had
16、finished the novel.,九、表示“关于”的about和on 两者都有“关于”的意思，不过前者为一般用词，而后者为较正式的“论述”。如：He came to tell me about something important./ He wrote a book on science. 十、between, among 一般说来，between表示两者之间，among用于三者或三者以上的中间。如：You are to sit between your father and me./ He is always happy among his classmates. 注意：但有时说的虽然是三个以上的人或东西，如果强调的是两两相互间接关系的，适用于between。如：Agreements were made between the different countries.在谈到一些事物或一组事物，而把它们视为分居两边时用between。如：The little valley
