NO.1 概念表语从句是在复合句中作表语的名词性从句.放在系动词之后,一般结构是主语 系动词 表语从句可以接表语从句的连系动词有be, look, remain, seem等.，我来为大家讲解一下关于英语语法讲解之定语从句?跟着小编一起来看一看吧!
英语语法讲解之定语从句
NO.1 概念
表语从句是在复合句中作表语的名词性从句.放在系动词之后,一般结构是主语 系动词 表语从句可以接表语从句的连系动词有be, look, remain, seem等.
可以接表语从句的系动词有：
1.be（being,been,am,is,are,was,were)
2. feel , seem , look, appear ,sound, taste , smell
3. stand , lie , remain ,keep, stay
4. become ,get , grow , turn ,go ,come, run, fall
5. prove, turn out
The trouble is that we are short of money.困难是我们资金短缺.
That is why stone walls are used instead of fences around New England fields.这就是为什么在新英格兰用石头墙而不用栅栏的原因.
At that time, it seemed as if I couldn't think of the right word anyhow.当时,我似乎怎么也想不出一个恰当的字眼来.
NO.2引导表语从句的词
从属连词that、whether、as though、 as if
关系代词who, what, which, whom, whose, whatever, whoever, whomever, whichever等；
关系副词when, where, why, how, however, whenever, wherever等.
由从属连词that，whether引导的表语从句
that在引导表语从句时无词义，而whether有词义，意为：是否.这时主句的主语常常是些抽象名词，如question(问题)，trouble(麻烦)，problem(问题)，result(结果)，chance(可能性)，suggestion(建议)，idea(想法)，reason(理由)等.表语从句对主句主语进行说明、解释，使主语的内容具体化.例如：
The trouble is (that) she has lost his money. 麻烦的事是他丢了钱.
The question is whether we need more ice cream.问题是我们是否还需要一些冰淇淋.
The problem was that it was too valuable for everyday use.问题是它作为日常之用太贵重了.
What she couldn’t understand was that fewer and fewer students showed interest in her lessons. 我们不能理解越来越少的学生对他的课不感兴趣.
由关系代词引导的表语从句
关系代词who, what, which, whom, whose, whatever, whoever, whomever, whichever等引导表语从句，在句中作主语、宾语、表语，关系代词不能省略.例如：The question is which of us should go.问题是我们哪一个应该去.
The problem was who could do the work.问题是谁能做这项工作.
That's what he is worrying about.那就是他在担心的事.That's what we should do.那是我们应该做的.
由关系副词引导的表语从句
关系副词 when, where, how, why 除在句子起连接作用外，在从句中还充当时间，地点，方式或原因状语，本身具有词义.例如：Go and get your coat. It's where you left it. 去把雨衣拿来.就在你原来放的地方.
I had neither a raincoat nor an umbrella. That’s why I got wet through. 我们既没伞也没雨衣，这是我们淋湿的原因.
That is what he is worried about.那就是他所担心的.
由连词because，as if/as though等引导的表语从句
It looked as if it was going to snow.看起来好像要下雪了.
That's because we never thought of it.这是因为我们从未想过此事.
It seems as if he didn’t know the answer.好像他不知道答案.
NO.3 注意
A. 表语从句一定要用陈述语序.
False: The question is when can he arrive at the hotel. Right: The question is when he can arrive at the hotel.
B. 不可以用if，而用whether 连接表语从句(as if 例外）
False: The question is if the enemy is marching towards us.
Right: The question is whether the enemy is marching towards us.
Right: It looked as if he had understood this question.
C.在有表语从句的复合句中，主句时态和从句时态可以不一致.
Right: The question is who will travel with me to Beijing tomorrow.
Right: The question is why he cried yesterday.
D. that在表语从句中不可以省掉.
NO.4基本用法
表语从句只能置于主句之后，而主句的动词只能是联系动词.名词性从句在be等系动词后作表语时被称为表语从句
例如：The problem is how we can get the things we need.
问题是我们怎样能弄到我们需要的东西. (how 在表语从句中充当方式状语)
The scissors are not what I need. 这把剪刀不是我所需要的.(what 在表语从句中充当宾语)
What I told him was that I would find him a good play. 我告诉他的是我会给他找个好剧本.(what在主语从句中作直接宾语, that作为表语从句的引导词在该表语从句中不充当句子成分，不能省略)
That is what I want to tell you.那就是我想要对你讲的.(what在表语从句中充当直接宾语)
That is why she failed to pass the exam. 那就是她考试不及格的原因.(why 在表语从句中充当原因状语)
What I told him was that I would find him a good play. 我告诉他的是我会给他找个好剧本.(what在主语从句中作直接宾语, that作为表语从句的引导词在该表语从句中不充当句子成分, 不能省略)
That is what I want to tell you.那就是我想要对你讲的.(what在表语从句中充当直接宾语)
That is why she failed to pass the exam. 那就是她考试不及格的原因.(why 在表语从句中充当原因状语)
注意
That is why...是常用句型, 意为这就是„„的原因/因此„„, 其中why引导的名词性从句在句中作表语, 该句型通常用于针对前面已经说明过的原因进行总结, 又如：
That is why you see this old woman before you know, Jeanne. 珍妮, 这就是现在这个老太婆出现在你面前的原因.
That is why I came. 这就是我来的原因.
下面是两个与That is why...形式相似的结构, 它们与That is why...结构之间的关系要能够辨析清楚：
(1)That is why...与That is the reason why...同义, 只不过从语法结构上讲, That is the reason why...中why引导的是—个定语从句, 将其中的the reason去掉则与That is why...结构一样, 例如：
That is (the reason) why I cannot agree. 这就是我不能同意的理由.
(2)That is because...句型中从属连词because引导的名词性从句在此作表语, 这也是个常用句型, 意为这就是为什么„„/因为„„.That is because...与That is why...之间的不同在于That is because...指原因或理由, That is why...则指由于各种原因所造成的后果, 例如：
He did not see the film last night. That is because he had to help his little sister with her homework.昨天晚上他没有去看电影, 那是因为他得帮助他的妹妹做作业.(第一句话说明结果, 第二句话说明原因)
He had seen the film before. That is why he did not see it last night.他以前曾看过那部电影, 因此他昨天晚上没有去看.(第一句话说明原因, 第二句话说明结果)
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