倒装的情况在英语中比较常见，也比较复杂，大致有以下几种：第一，疑问句一般都用倒装，这个谁都知道。第二，表示否定或基本否定的词、词组放在句首作状语时。这种情况下倒装到主语前的通常是助动词、情态动词或动词BE。如：1. never before has anyone applied such principles to practice. 2. rarely did tom leave his lab those days.第三，only引出的状语放在句首时，这种情况下的倒装一般是部分倒装。如： 1. only then did the doctor realize that his patient needed surgery. 2. only when you adjust down your price to some extent can we conclude the business.还有几种情况，今天有事，改天再说。或者请其他的吧友补充吧。