雅思阅读名词性从句是烤鸭们必须掌握的一个知识点，下面分享了相关的定义和备考方法，大家可以参考一下。
一、名词性从句的定义和分类
在句中起名词作用的句子叫做名词性从句，该从句能作为主语、宾语、表语、同位语、介词宾语等成分。所以，相应地，名词性从句有四个分类：主语从句、宾语从句、表语从句和同位语从句。
通常从句都需要有相应的连接词，名词性从句也不例外。常见的名词性从句连接词可以分为三类：1. 不做任何成分的连接词：that、whether/if、as if/as though;2. 连接代词：what、whatever、who、whoever、whom、whomever、whose、whosever、which、whichever;3. 连接副词：when、whenever、where、wherever、how、however、why。
二、名词性从句的用法讲解
1、 主语从句：主语从句就是在复合句中充当主语成分的句子。常见的主语从句的连接词有that、whether、who、when、how等。主语从句的时态一般不受主句时态的影响和限制。同学们还需要注意的是英语中为了避免头重脚轻，经常会把主语从句放在后面，用一个形式主语来代替。给大家举个例子吧：
It will never be known how and when this numeration ability developed, but it is certain that numeration was well developed by the time (that) humans had formed even permanent settlements. (剑 6 Test 2 passage 3)
句子结构分析：主语是it，指代后面的由两个特殊疑问词how and when引导的主语从句，谓语是will never be known，but表转折，第二个it作形式主语，指代后面的that主语从句，系动词是is，表语是certain。humans had formed…在这个句子是省略了that的定语从句，修饰the time。
2、 表语从句：表语从句很简单， 一般的结构为：主语+连系动词+句子作表语。常见的连接词有that、what、who、when、where、which、why、whether、how等。表语从句的时态也不受主语时态的影响和限制。举个例子吧：
That is mainly because the costs of all this damage are what economists refer to as externalities: they are outside the main transaction, which is for example producing and selling a field of wheat, and are borne directly by neither producers nor consumers.(剑 7 Test 2 Passage 2)
句子结构分析：that指代上文，人们意识不到食品的隐藏经济代价。这句话的主干是That is mainly because…，because引导表语从句，what引导从句中的表语从句，冒号后面是对术语外部经济效应的解释说明。冒号后面句子的主干是they are outside the main transaction，which引导非限制性定语从句修饰前面的句子。
3、 宾语从句：宾语从句应该是大家最常见的一种名词性从句了，常位于及物动词、介词、复合谓语或者形容词后。常见的连接词有that、 if/whether、who、what、why、how、when、whichever等。大家可以看看下面这个例子：
MIRTP focused on what would be most appropriate for the inhabitants of Makete in terms of what was available, how much they could afford and what they were willing to accept.(剑 7 Test 2 Passage 3)
句子结构分析：句子主干是MIRTP focused on what…。in terms of what…how much…and what they…。这句话中出现了四个特殊疑问词：三个what一个how much，因为它们都是在介词之后，所以引导的都是宾语从句。
4、 同位语从句：同位语从句一般是对一个内涵丰富的抽象名词(比如说news、idea、fact、promise、question、thought、hope等)进行解释说明。常用的连接词有that、whether、what、who、how、when、where等。给大家举个例子吧：
Lozanov's instructional technique is based on the evidence that the connections made in the brain through unconscious processing (which he calls non-specific mental reactivity) are more durable than those made through conscious processing. (剑7 Test 4 Passage 3)
句子结构分析：这句话的主语是Lozanov's instructional technique， is based on表被动语态， 第一个that引导的从句是evidence的同位语从句，该同位语从句的主干是the connections are more durable than those…。两个made都作后置定语，分别修饰connections和those，which 引导限制性定语从句修饰processing。
上面就是对雅思阅读中名词性从句的具体介绍，希望对大家雅思备考有帮助。最后，小编预祝大家考出满意的雅思成绩。
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