倒装句是一种把动词（助动词）移动到主语前，起到强调、增强清楚与简洁性功能的句子。
一、比较级倒装
Girls like cats more than boys, who as a rule are a cruel lot, do.
这一句中修辞不佳，句尾的do无法省略，否则句子有歧义，但是这个助动词离它的主语boys又太远了。我们使用倒装：
Girls like cats more than do boys, who as a rule are a cruel lot.
总结：比较级使用倒装
1> 从属从句中的助动词或be动词不宜省略；
2> 主语后面有较长的修饰语。
二、关系从句的倒装
关系词必须先向前移动照成顺序反常的时候才使用倒装
句1：The President is a man.
句2：A heavy responsibility, whether he likes it or not, falls on him.
两句联合：
The President is a man on whom a heavy responsibility whether he likes it or not, falls.
on whom是一个介词短语修饰falls，但是 移动到句首以后同falls的距离相隔太远了，同时falls的主语a heavy responsibility同falls的距离也太远，就需要使用倒装句：
The President is a man on whom falls a heavy responsibility whether he likes it or not.
注意：如果关系词原本就在句首的位置，没有移动，就不能使用倒装。
三、假设语气的倒装
假设语气往往是使用if引导的，如果有be动词和助动词就可以将其移动到主语前面，省略连接词。形成倒装：
If I had been there, I could have done something to help.
为了加强简洁形成倒装：
Had I been there, I could have done something to help.
四、引用句的倒装
直接引用：
The police said, "None was killed in the accident."
将引用的话放于前面，起到强调的作用：
"None was killed in the accident." said the police.
间接引用：
The WHO warns that cholera is coming back.
将最重要的放在前面，形成倒装：
Cholera, warns the WHO, is coming back.
五、地方副词倒装
这种倒装是把地方副词放于句首，起强调作用。
There goes the train!
Here is your ticket for the opera!
这里是把there和here地方副词放于句首的倒装。其他的地方副词也可以：
In Loch Ness dwells a mysterious monster.
六、否定副词开头的倒装
表示否定的副词（not、never、hardly、barely）放于句首强调语气，就得使用倒装
We don't have such luck every day.
如果把not every day放于句首强调不是每一天，就得使用倒装：
Not every day do we have such luck.
另外有一些副词hardly、barely移动到句首也要使用倒装：
I had hardly sat down to work when the phone rang.
将hardly移动到句首起加强语气的作用：
Hardly had I sat down to work when the phone rang.
注意：如果hardly在句首是正常的修饰词，而不是起强调作用的，就不能使用倒装句。
not only……but also配合形成倒装就比较复杂，我们相信说明一下：
He not only passed the exam but also scored at the top.
not only……but also形成句子要求对仗工整，我们先来尝试一下：
Not only did he passed the exam but also scored at the top.
前半句not only引导的从句我们改成了倒装，但是与后面but also的句子不对称，我们修改成：
Not only did he passed the exam but also he scored at the top.（不佳）
我们经常将not only和but also连在一起背诵，但是不知道only和also都是焦点副词，有一种强调的功能。这时候就应该拆开but also，使得also强调后面的scored at the top：
Not only did he passed the exam but he also scored at the top.
