高中英语语法:连词

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     连词是一种虚词,分为并列连词和从属连词两大类。并列连词是连接主语与主语,谓语与谓语,句子与句子,分词与分词的词,它要求前后两部分有相同的形式和语法作用;而从属连词一般连接主句与从句,从句形式有名词性从句,定语从句和状语从句等。

(一)并列连词

     并列连词可用来连接词与词,词组与词组,分句与分句。常用的并列连词有:and(和),as well as(既…又),both … and(不但…而且),not only … but also(不但…而且),not … but(不是…而是),neither … nor(既不…也不),either … or(不是…就是),or(或者),but (但是),yet(然而),for(因为),so(所以),while(而),when(这时)等。如:
  Both my brother and my sister are teachers.
  His room is bright but mine is gloomy(暗沉沉的).
  He can not only repair radios but also fix them.
  It is a glorious(光荣的)yet difficult task./ Strike while iron is hot.

(二)从属连词

     从属连词是指在复合句中引导从句的连结词。常见的从属连词有:
  引导时间状语从句的:after, before, when, as, while, since, until, till, as soon as
  引导原因状语从句的:because, since, as
  引导让步状语从句的:although, though, no matter(无论), even if (though)
  引导条件状语从句的:if, unless, once, so (as) long as
  引导结果状语从句的:so … that …, such … that …
  引导目的状语从句的:so that …, in order that …
  引导比较状语从句的:as … as …, not so (as) … as …, … than …
  引导方式状语从句的:as if …
  引导主语,宾语或表语从句的连词主要有:that, whether, if三个。其中that 和whether间或还可以引起同位从句和状语从句。

(三)某些用法比较特殊的从属连词用法区别

1、当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;
② when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 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./ She’ll 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:I’ll come when (if) I’m free.
2、before作连词一般表示时间,意为“在…之前”,但有些句子中这样译就显得别扭。试看以下句子的翻译:He almost knocked me down before he saw me.他几乎把我撞倒才看见我;Before I could get in a word he had measured me.我还没来得及插话,他已经给我量好了尺寸。