英语句子主语与谓语通常有两种语序，一种是主语位于谓语之前即自然语序，另一种是谓语位于主语之前即倒装语序。把整个谓语置于主语前叫全部倒装，把复合谓语的一部分(助动词或情态动词)置于主语之前叫部分倒装。
一、部分倒装①在疑问句
Can you spell the word for me?
②否定词位于句首
No sooner had she gone out than a student came to visit her.
③only加状语位于句首
Only by increasing the number of doctors by 50 percent can the patient be treated properly in this hospital.
④so加状语位于句首
So loudly did the students read their lessons that people could hear them out in the field.
⑤as引导的让步状语从句
Child as he is, he has to make a living on his own.（表语提到主语前面）
⑥虚拟语气中从句if省略
Had he spent more time practicing speaking English before, he would be able to speak it much better now.
二、全部倒装①用于现存句型中
At the top of the hill there stands an old temple.
②状语置于句首，谓语表示行动去向的动词
Out rushed a tiger from among the bushes.
③表语置于句首
Among the crises that face humans is the lack of natural resources.
