英语学科知识点：虚拟语气思维导图

1.与现在事实相反：①条件从句谓语：动词过去式(be 一般用were)

2.与过去事实相反：①条件从句谓语：had+过去分词

3.与将来事实相反：(1)条件从句谓语：①动词过去式②should+动词原形③were to+动词原形

条件从句的动作和主句的动作发生的时间不一致(如一个是过去发生的，一个是现在发生的)。这时主从句动词的形式要根据时间来调整，使用各自的谓语动词。

例如： Tom would be alive today if the doctor had come sooner last night.

If 条件句中有were, had(助动词)和should时，可使用倒装结构，但if必须省略。

If I had seen him then, I would have been very happy. =Had I see him then, I would have been very happy.

若条件从句为否定句，否定词not应置于主语之后，而不能与were, should, had 等缩成weren’t, shouldn’t, hadn’t而置于句首。

If I were not so busy, I would go with you. =Were I not so busy, I would go with you.

用without(=but for)，or (else)，otherwise暗示if从句

例如：but for his help, we wouldn’t have made such great progress.

当上下文或上下句中的语境暗示的时候，省略条件句，避免重复。

It was not a matter of money. Even a very poor man would have done the same, I think.

If it weren’t for…和if it hadn’t been for…是两个很正常的虚拟语气句型，其意为若不是(有);要不是有。

其倒装形式是：Were it not for…和Had it not been for…

此句型可与but for, without "要不是’(后加名词，句子谓语动词常与虚拟语气)等替换。