同学，你好！
以下是有关名词性从句、倒装句和主谓一致三项语法的详细介绍，希望对你有所帮助。
一 名词性从句
所谓名词性从句，就是指其作用相当于名词的从句，它包括主语从句、表语从句、宾语从句和同位语从句。
（一）、主语从句
1. 引导词：主语从句就是在复合句中用作主语的从句，引导主语从句的引导词主要有三类：一是that；二是whether；三是那些可以用作疑问词的词语，如what, who, which, when, where, how, why等。如：
That we shall be late is certain. 我们要晚了，这是确定无疑的。
What he says is not important. 他说的话并不重要。
How this happened is not clear to anyone. 这件事怎样发生的，谁也不清楚。
Which side wins makes no difference to him. 哪边赢他都无所谓。
Whether it will do us harm remains to be seen. 是否对我们有害还要看一看。
2. 形式主语：有时为了避免句子显得“头重脚轻”，可用it作形式主语放在句首，而把真正的主语放在句末。如：
It’s a pity that he didn’t come. 很遗憾他没来。
It’s not yet known what she did. 她做什么还不得而知。
It was uncertain whether he could come or not. 他是否会来还不肯定。
这三句句首的it均为形式主语，相应的真主语分别是that he didn’t come / what she did / whether he could come or not。
（二）、表语从句
表语从句就是在复合句中用作表语的从句。一般说来，可用于引导主语从句的引导词也可用于引导表语从句，如that, what, who, which, when, where, how, why, whether等。如：
My idea is that we should do it right away. 我的意见是马上就干。
That is what he meant. 这就是他的意思。
The problem is how we can find him. 问题是我们如何找到他。
The morning is when I’m busiest. 早上是我最忙的时候。
That’s where you are wrong. 这就是你不对的地方。
That’s why he didn’t come. 这就是他没有来的缘故。
另外，表语从句还可以用as if, as though, because等来引导。如：
It is because he is too foolish. 那是因为他太蠢了。
It is not as though we were poor. 又不是我们家里穷。
三、宾语从句
1. 引导词：宾语从句就是在复合句中用作宾语的从句。一般说来，可用于引导主语从句的引导词也可用于引导宾语从句，如that, what, who, which, when, where, how, why, whether等。如：
We believe that he is honest. 我们相信他是诚实的。
She has got what she wanted. 她要的东西得到了。
I haven’t decided whether I should go. 我还没决定我是否会去。
I asked how he was getting on. 我问他情况怎样。
He asked when the train would get in. 他问火车什么时候进站。
He asked me where I was going. 他问我到哪儿去。
Please tell me which you like. 告诉我你喜欢哪一个。
He asked who lived next door. 他问谁住在隔壁。
She asked why he was silent. 她问他为什么一言不发。
2. if与whether：if通常不用于引导主语从句或表语从句，但可以用于引导宾语从句，与whether用法相同，常可互换。如：
I wonder if it’s large enough. 不知它是否够大。
She didn’t say if he was still alive. 她没说他是否还活着(
www.yywords.com)。
但是，当于用于介词后引导宾语从句时，只能用whether，不能用if。如：
I worry about whether I hurt her feelings. 我为是否伤了她的感情而忧虑。
3. that的省略：that引导主语从句或表语从句时通常不省略，但引导宾语从句时通常可以省略。如：
She said (that) she didn’t want to know. 她说她不想知道。
I don’t think (that) she’s interested in it. 我想她对这事没有兴趣。
4. 否定转移：当主句主语为第一人称，且主句谓语动词为think, believe, suppose, expect, imagine等时，若其后接一个表示否定意义的宾语从句，此时通常应将否定转移到主句上。如：
I don’t think that he will leave. 我认为他不会离开。
I don’t believe that it is easy. 我相信这不会容易。
四、同位语从句
在复合句中用作同位语的从句叫同位语从句。所谓同位语，就是指两个语法单位指同一个人或事物，并且句法功能也一样，此时我们就把后一项称为前一项的同位语。所谓同位语从句，就是指用于名词后对该名词的内容进行说明解释的从句。如：
The judge paid no attention to the fact that she had just lost her husband. 法官毫不考虑她刚刚失去丈夫一事。
句中的that she had just lost her husband为修饰名词the fact的同位语从句，用以具体说明the fact的内容。
Mary suddenly got the feeling that someone was watching her. 玛丽突然感到有人在看她。
句中的that someone was watching her为修饰名词the feeling的同位语从句，用以具体说明the feeling的内容。
英语中只有少数名词可后接同位语从句，比较常见的有belief, doubt, fact, feeling, hope, idea, message, news, opinion等(
www.yygrammar.com)。
另外，同位语从句的引导词也比较有限，主要是由that引导，有时可也可用when, how, where, whether, who等引导，但是不能用if也引导，也不能用what来引导。如：
You have no idea how worried I was! 你不知道我多着急!
He had no idea why she left. 他不知道她为什么离开。
There is some doubt whether he will come. 他是否会来还不一定。
二 倒装句
英语的基本句型是主语 + 谓语。如果将主语与谓语调换,
称倒装句。
装句分全倒装句和半倒装句。
一、
全倒装:
主语与谓语交换位置不需任何助动词,
叫全倒装。全倒装有以下三种情况:
1、当here,
there, out, in, up, down等副词放在句首时,
句子需全倒装:
There
goes the bell! 铃响了！ There
lived an old man. Here
comes the bus.注意: ①在这种情况下倒装仅限于不及物动词或be动词,
像go,
come, mush等。 ②主语如果是代词时不需倒装如Away
he went. 他走远了。
2、方位状语在句首,
如:
In
front of the house stopped a police car.
Nearby
were two canoes in which they had come to the island.
Under
the tree sat a boy.
3
、直接引语在句首,
这种情况可倒装也可不倒装
"What
does it mean?" asked the boy或the
boy asked.
二、半倒装:
主语与谓语的助动词交换位置称半倒装,
有以下数种情况:
1,否定意义的词在句首,
句子半倒装,
例如:
little, never, not, no, hardly, rarely,seldom
Never
shall I forget you. At
no time was the man aware of what was happening.
Little
did I understand what he said to me at that time.
2、
几对并列连词如not
only…but also, hardly… when等连接两个并列句,
连词在句首,
前句半倒装,
后句不倒装:
Not
only was everything he had taker away from him, but also his German citizenship
was taken away.
No
sooner had I got to the bus stop than the bus started.
注意:
①not
only…but also连接两个并列主语时不需倒装,
如:Not
only you but also I like playing chess.
②neither…nor在句首时,
前后两句都需倒装,Neither
do I have a sister nor does my husband.
3、only在句首强调状语,
主句半倒装:
Only
then did I realize that I was wrong.Only in this way can I learn from my
fault.
Only
when the war was over in 1918, was he able to get back to
work.
注意:
only强调主语不倒装:Only
the teachers can use the room.
4、so…that句型,
so在句首时,
主句倒装,
that从句不倒装:
So
easy is it that a clild can learn it.So hard did he work that he finally won the
fame.
I
saw the film, so did he.
5.省略了if的虚拟条件句
Had
I been informed earlier, I could have done something.Were she here, she would
support the motion.
三 主谓一致
在英语句子里，谓语受主语支配，其动词必须和主语在人称和数上保持一致，这就叫主谓一致。寻其规律，大致可归纳为三个原则，即语法一致、逻辑意义一致和就近一致原则。
一、语法一致原则
语法上一致就是谓语动词和主语在单、复数形式上保持一致。
1. 以单数名词或代词、动词不定式短语、动名词短语或从句作主语时，谓语动词一般用单数形式；主语为复数时，谓语动词用复数形式。如：His father is working on the farm. / To study English well is not easy. / What he said is very important for us all. / The children were in the classroom two hours ago. / Reading in the sun is bad for your eyes.
注意：由what引导的主语从句，后面的谓语动词多数情况用单数形式，但若表语是复数或what从句是一个带有复数意义的并列结构时，主句的谓语动词用复数形式。如：What I bought were three English books. / What I say and do is （are） helpful to you.
2. 由连接词and或both …… and连接起来的合成主语后面，要用复数形式的谓语动词。如：Lucy and Lily are twins. / She and I are classmates. / The boy and the girl were surprised when they heard the news. / Both she and he are Young Pioneers.
注意：（1）若and所连接的两个词是指同一个人或物时，它后面的谓语动词就应用单数形式。如：The writer and artist has come. （2）由and连接的并列单数主语前如果分别有no， each， every more than a （an） ， many a （an）修饰时，其谓语动词要用单数形式。如：Every student and every teacher was in the room. / No boy and no girl likes it.
3. 主语为单数名词或代词，尽管后面跟有with， together with， except， but， like， as well as， rather than， more than， no less than， besides， including等引起的短语，谓语动词仍用单数形式；若主语为复数，谓语用复数形式。如：Mr. Green， together with his wife and children， has come to China. / Nobody but Jim and Mike was on the playground. / She， like you and Tom， is very tall.
4. either， neither， each， every 或no +单数名词和由some， any， no， every构成的复合不定代词，都作单数看待。如：Each of us has a new book. / Everything around us is matter.
注意：（1）在口语中当either或neither后跟有“of+复数名词（或代词）”作主语时，其谓语动词也可用复数。如：Neither of the texts is （are） interesting. （2）若none of后面的名词是不可数名词，它的谓语动词就要用单数；若它后面的名词是复数，它的谓语动词用单数或复数都可以。如：None of us has （have） been to America.
5. 在定语从句时，关系代词that， who， which等作主语时，其谓语动词的数应与句中先行词的数一致。如：He is one of my friends who are working hard. / He is the only one of my friends who is working hard.
6. 如果集体名词指的是整个集体，它的谓语动词用单数；如果它指集体的成员，其谓语动词就用复数形式。这些词有family， class， crowd， committee， population， audience等。如：Class Four is on the third floor. / Class Four are unable to agree upon a monitor.
注意：people， police， cattle等名词一般都用作复数。如：The police are looking for the lost child.
7. 由“a lot of， lots of， plenty of， the rest of， the majority of + 名词”构成的短语以及由“分数或百分数+名词”构成的短语作主语，其谓语动词的数要根据短语中后面名词的数而定。如：There are a lot of people in the classroom. / The rest of the lecture is wonderful. / 50% of the students in our class are girls.
注意：a number of“许多”，作定语修饰复数名词，谓语用复数；the number of“……的数量”，主语是number，谓语用单数。
8. 在倒装句中，谓语动词的数应与其后的主语一致。如：There comes the bus. / On the wall are many pictures. / Such is the result. / Such are the facts.
二、逻辑意义一致原则
逻辑意义一致就是谓语动词的数必须和主语的意义一致（因有时主语形式为单数，但意义为复数；有时形式为复数，但意义为单数）。
1. what， who， which， any， more， all等代词可以是单数，也可是复数，主要靠意思来决定。如：Which is your bag？ / Which are your bags？ / All is going well. / All have gone to Beijing.
2. 表示“时间、重量、长度、价值”等的名词的复数作主语时，谓语动词通常用单数形式，这是由于作主语的名词在概念上是一个整体，如：Thirty minutes is enough for the work.
3. 若英语是书名、片名、格言、剧名、报名、国名等的复数形式，其谓语动词通常用单数形式。如：“The Arabian Nights” is an interesting story-book.
4. 表数量的短语“one and a half”后接复数名词作主语时，其谓语动词可用单数形式（也可用复数。如：One and a half apples is （are） left on the table.
5. 算式中表示数目（字）的主语通常作单数看待，其谓语动词采用单数形式。如：Twelve plus eight is twenty. / Fifty-six divided by eight is seven.
6. 一些学科名词是以 –ics 结尾，如：mathematics， politics， physics 以及news， works等，都属于形式上是复数的名词，实际意义为单数名词，它们作主语时，其谓语动词要用单数形式。如：The paper works was built in 1990. / I think physics isn‘t easy to study.
7. trousers， glasses， clothes， shoes， 等词作主语时，谓语用复数，但如果这些名词前有a （the） pair of等量词修饰时，谓语动词用单数。如：My glasses are broken. / The pair of shoes under the bed is his.
8. “定冠词the + 形容词或分词”，表示某一类人时，动词用复数。
三、就近一致原则
在英语句子中，有时谓语动词的人称和数与最近的主语保持一致。
1. 当两个主语由either …… or， neither …… nor， whether …… or ……， not only …… but also连接时，谓语动词和邻近的主语一致。如：Either the teacher or the students are our friends. / Neither they nor he is wholly right. / Is neither he nor they wholly right？
2. there be句型be动词单复数取决于其后的主语。如果其后是由and连接的两个主语，则应与靠近的那个主语保持一致。如：There are two chairs and a desk in the room.
注意：Here引导的句子用法同上。