had开头的否定虚拟语气

had是have的过去式

否定形式：在had的后面加not，表示为had not。

Had 一般放在句首是表示虚拟，但是是倒装的用法.

比如说Had I had time， I would have done that yesterday.的原来的顺序是If I had had time，I would have done that yesterday.这里将had提前构成倒装句，句意是一样的.

had开头的否定虚拟语气

Had开头的句子往往是对过去的虚拟条件句采用倒装的结构。