过去完成时,也称为“过去的过去”,主要用于表示在过去某个时间点之前发生的事情或完成的动作。'had'在这种时态中是不可或缺的,主要用于表示两个动作在过去发生的先后顺序,描述在过去某个时间点之前已经完成的动作,表示假设条件,以及表示对过去的感叹和遗憾。使用时,'had'后面要加动词的过去分词形式。
1. 表示先后顺序
过去完成时经常用于表示两个动作在过去发生的先后顺序,这时had通常与before或after连用。例如:
- I had finished my homework before my parents came home.
- After I had eaten breakfast, I went for a walk.
2. 表示“过去的过去”
当我们需要描述在过去某个时间点之前已经完成的动作时,通常使用过去完成时。例如:
- By the time I arrived at the cinema, the movie had already started.
- She had written three novels before she turned 30.
3. 表示假设条件
过去完成时也可以用于表示假设条件,通常与if连用。例如:
- If I had studied harder, I would have passed the exam.
- If she had known the truth, she wouldn't have made that decision.
4. 表示感叹和遗憾
有时候,我们会用过去完成时来表示对过去的感叹和遗憾。例如:
- I wish I had known about the sale earlier. I would have saved a lot of money.
- Had I realized the importance of exercise earlier, I would have started working out years ago.
在使用过去完成时时,需要注意的是,had后面要加动词的过去分词形式。例如:had eaten,had gone,had studied等等。