【过去完成时的标志词有哪些】在英语语法中，过去完成时（Past Perfect Tense）用于表示在过去某一时间或动作之前已经发生或完成的动作。为了准确判断一个句子是否使用了过去完成时，我们可以通过一些常见的“标志词”来辅助识别。
以下是对过去完成时常见标志词的总结，并以表格形式展示，帮助学习者更好地理解和记忆。
一、过去完成时的标志词总结
1. already
表示“已经”，强调某个动作在另一个过去动作之前已完成。
例：He had already left when I arrived.
2. yet
常用于否定句和疑问句中，表示“到那时为止还未”。
例：Had you finished your homework yet?
3. just
表示“刚刚”，强调动作刚刚发生。
例：She had just eaten when the phone rang.
4. before
表示“在……之前”，常与过去时连用。
例：They had left before I got there.
5. by that time
表示“到那时为止”，强调在某个时间点之前完成的动作。
例：By that time, we had already decided to go.
6. by the time + 过去时间
表示“到……的时候”，强调在某个具体时间点前已经完成的动作。
例：By the time we reached the station, the train had left.
7. after
表示“在……之后”，通常与过去时连用。
例：He had finished his work after he came back.
8. no sooner... than...
表示“一……就……”，强调两个动作几乎同时发生。
例：No sooner had he arrived than it started to rain.
9. as soon as
表示“一……就……”，也常与过去完成时连用。
例：As soon as she had opened the door, she saw him.
10. when
引导时间状语从句，表示“当……时”，常用于过去完成时结构中。
例：When I got home, she had already gone to bed.
二、过去完成时标志词表格
| 标志词 | 用法说明 | 例句 |
| already | 表示“已经”，强调动作已完成 | He had already left when I arrived. |
| yet | 否定句或疑问句中，表示“尚未” | Had you finished your homework yet? |
| just | 表示“刚刚”，强调动作刚发生 | She had just eaten when the phone rang. |
| before | 表示“在……之前” | They had left before I got there. |
| by that time | 表示“到那时为止” | By that time, we had already decided to go. |
| by the time | 表示“到……的时候” | By the time we reached the station, the train had left. |
| after | 表示“在……之后” | He had finished his work after he came back. |
| no sooner... than... | 表示“一……就……” | No sooner had he arrived than it started to rain. |
| as soon as | 表示“一……就……” | As soon as she had opened the door, she saw him. |
| when | 引导时间状语从句 | When I got home, she had already gone to bed. |
通过掌握这些标志词，可以帮助我们在阅读或写作中更准确地识别和使用过去完成时。需要注意的是，这些词通常需要结合上下文来判断是否使用过去完成时，而不能单独依赖标志词。
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