【在时间和条件状语从句中】在英语语法中，时间状语从句和条件状语从句是两种非常常见的从句类型，它们在句子中起到补充说明主句动作发生的时间或条件的作用。掌握这两种从句的结构与用法，有助于提高英语表达的准确性和逻辑性。
一、时间状语从句
时间状语从句用来表示主句动作发生的时间，常见的引导词有：when, while, as, before, after, until, since, once, by the time, as soon as 等。
| 引导词 | 含义 | 例句 |
| when | 当……时候 | When I arrived, he was already leaving. |
| while | 当……时（强调同时发生） | While I was cooking, the phone rang. |
| as | 当……时（强调同时进行） | As I walked, I heard someone calling me. |
| before | 在……之前 | He left before I could say goodbye. |
| after | 在……之后 | We started the meeting after the boss arrived. |
| until | 直到…… | She waited until the rain stopped. |
| since | 自从……以来 | I have lived here since 2015. |
| once | 一旦…… | Once you understand, it's easy. |
| by the time | 到……时候为止 | By the time we got there, the movie had started. |
| as soon as | 一……就…… | As soon as she saw me, she smiled. |
二、条件状语从句
条件状语从句用于表达某种假设或前提，常见引导词包括：if, unless, as long as, provided that, in case, suppose/supposing that 等。
| 引导词 | 含义 | 例句 |
| if | 如果 | If it rains, we will stay home. |
| unless | 除非 | Unless you study, you won't pass. |
| as long as | 只要 | As long as you work hard, you can succeed. |
| provided that | 假如 | Provided that you are ready, we can leave now. |
| in case | 以防 | In case you forget, I’ll remind you. |
| suppose/supposing that | 假设 | Suppose you have a chance, what would you do? |
三、总结
时间状语从句主要关注动作发生的时间关系，常使用 when, while, as, before, after 等连接词；而条件状语从句则关注动作发生的前提或假设，常用 if, unless, as long as, provided that 等引导词。
两者在实际应用中都非常重要，尤其在写作和口语中，合理使用这些从句可以使表达更加自然、逻辑更清晰。
通过以上表格和内容的整理，可以系统地掌握时间和条件状语从句的基本结构与用法，帮助学习者在实际语言运用中灵活运用。
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