【编者按】精品学习网英语四六级频道为大家收集整理了“四六级常考语法精讲”供大家参考，希望对大家有所帮助!
1. 常考的几种倒装结构
1) 当表示否定或基本否定的词或词组位于句首作状语时用倒装。这类词或词组常用的有：never, nowhere, seldom, rarely, little, hardly, scarcely, barely, not until, not only, by no means, in no time, under no circumstances, under no condition, in no way, in no case, at no time, on no account等。
Never have I heard it before.
Nowhere can I find my lost watch.
Under no circumstance should a student cheat in the exam.
Not only was Churchill a statesman, but also a poet.
Note: 当 “no sooner … than”和“hardly/scarcely … when/before”位于句首时用倒装。该结构表示“一…就…”，在时态上主句一般用过去完成时，when或than引导的从句用一般过去时。
Hardly/Scarcely had I got home when/before the bell rang.
No sooner had the performance begun than the lights went out.
2) 当here, there, then, thus, only, hence, little等副词位于句首，句中主、谓用倒装。
Here is the book for you.
There goes the bell.
Then came the order to take off.
Thus arose the division between the developed and developing countries.
3) 当 “so/such … that”结构中的so或such 位于句首时用倒装。
So cold was it at night that I could hardly fall asleep.
Such was the force of explosion that all the windows were broken.
4) 分句以so, neither, nor, no more等副词位于句首，表明前面句子中所说明的情况也使用于后面的句子时用倒装。
Copper is a good conductor. So are many other metals.
He didn’t see the film last night, neither did she.
2. 强调句型
这里讲的强调句主要是以it为引导词的分裂句。其构成形式为：It is (was) +被强调部分+ that(who, which) + 句子的其他部分。被强调的部分通常为主语、宾语和状语。
It is only when one is ill that one realizes the value of health.
It is what you will do that is essential.
Note:
在被强调部分的后面，一般用that引出句子的其他部分。但是如果强调的部分是表示人的名词，那么也可用who;如果是指物的名词也可用which。
It was Jane that/who lent me the money.
It was this novel that/which they talked about last night.
如果强调的是原因状语从句，只能用because引导，不能由since, as或why引导。
It was because(不用since或as) he had never had the opportunity that John hadn’t learned to drive.
有三类句子成分不可以进行强调，即表语、谓语动词和由though, although, whereas等引导的从句。
It is although he is young that he can speak four languages. (误)
Although he is young, he can speak four languages. (正)
It is whereas he prefers pop song that I like classical music. (误)
I like classical music whereas he prefers pop songs. (正)
3. 使役动词后的宾语补足语
使役动词除了要有宾语之外还要加上宾语补足语才能使句子的意义完整。常用的使役动词有：have, want, make, get, leave, set, let等。可以担当使役动词宾语补足语的有名词，形容词，介词短语，动词不定式和分词等。
All work and no play makes Jack a dull boy.
A good night’s rest will set you right.