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根据在句中的功能名词性从句可分为主语从句、宾语从句、表语从句和同位语从句。因为它是从句，因此具有句子的特点，有主、谓成分,同时又具有名词性特点，这些从句和名词一样，在句中可以充当主语、宾语（包括介词宾语和动词宾语以及某些形容词后的宾语）、表语和同位语。名词性从句是中学英语学习的重点，也是高考的主要考点之一。 一、主语从句 1.分清引导主语从句的三类引导词：(1)that不充当句子成分，本身无意义，仅起连接作用，但不能省略，通常用it作形式主语。(2)who, whom, what, which, whoever, whatever, whichever本身有意义，在句中作主语或宾语,不能省略。(3)where, when, how, why本身有意义，在句中作状语。 2.注意whoever, whatever, whichever等引导主语从句的含义。 3.由it作形式主语的句型 (1)It + be + 形容词(obvious, natural, good, funny, etc.) +that 从句。 (2)It + be + 名词性词组(no wonder, an honour, a pity, no surprise, etc.)+that从句。 (3)It + be + 过去分词(said, reported, thought, expected, etc.)+ that从句。 （4）It + seem, happen 等不及物动词及短语的相应形式+that 从句。 （5）It doesn’t matter/makes no difference, etc.+连接代词或连接副词引导的主语从句。 注意：由what, whatever, whoever等引导的主语从句，必须置于主句的谓语动词之前，不能用it作形式主语。 What some people regard as a drawback is seen as a plus by many others. It is a fact that English is being accepted as an international language. 二、宾语从句 宾语从句在复合句中可以作动词的宾语，也可以作介词、某些形容词的宾语。 We should respect food and think about the people who don’t have what we have here and treat food nicely. 三、表语从句 1．that和whether引导的表语从句 that引导表语从句时，that本身没有词义，一般不可以省略（但在口语中有时也可以省略）。whether引导表语从句，表示"是否"，不能省略。 2．if一般不用来引导表语从句，但as if却可引导表语从句，如： All this was over twenty years ago, but it was as if it was only yesterday. 3.主语是reason时，表语从句常用that,不用because, 如： The reason why he didn’t come was that he was ill. Part of the reason Charles Dickens
loved his own novel, David
Copperfield, was that it was rather closely modeled on
his own life. 四、同位语从句 同位语从句一般由that（不能用which，且that不能省略）或whether引导，有时也可以用when, where, how, why等引导。同位语从句常放在名词的后面，解释说明该名词的具体内容。同位语从句修饰的名词必须是一个表示事实等的抽象名词，如：fact, news, idea,truth, hope, information, belief, reply, doubt等。 The question occurred to me
where we were to get the machines
repaired. 五、引导词whether和if的用法区别 通常引导主语从句、表语从句和同位语从句时，要用连词whether不用if；习惯上也只能说whether...or not，而不说if ...or not。 Whether the visiting president will come to our school is not known yet. 六、先行词与同位词从句分隔的现象 有时为了避免句子失衡而把同位语从句置后、谓语置前，这样就产生了先行词与同位语从句分隔的现象，此时考生要认真分析句子成分，分辨出同位语从句。 News came from the school office that Wang Lin had been admitted to Beijing University. 七、that引导的同位语从句与that引导的定语从句的区别 that引导同位语从句时是从属连词，只起连接作用，无意义，不充当句子成分，不可省略。而that在定语从句中为关系代词，不仅起连接作用，还充当句子成分，如果在定语从句中作宾语时可省略。如： The news that Mr. Li will be our new English teacher is true. 李先生将是我们的新英语老师,这个消息是真的。(同位语从句，that不可省) The news (that) he told me yesterday is true. 他昨天告诉我的消息是真的。(定语从句，that在从句中作told的宾语，可省略) Information has been put forward that more middle school graduates will be admitted into universities. |
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