[3]原因状语从句：because、since、as

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原因状语从句是用于说明主句动作或状态“为何发生”的从句，通常由特定从属连词引导，核心功能是补充“原因”这一逻辑背景。根据引导词的不同，可分为常用引导词类（如because, since, as）、特殊引导词类（如for, now that, considering that）等，各类引导词在语气强度、用法场景上存在差异。

一、常用引导词：because, since, as（语气强度递减）

这三类是最基础的原因状语从句引导词，核心区别在于语气强弱和逻辑侧重：

because：语气最强，表“直接、根本原因”，可回答“why”提问，常置于主句后（强调原因时可置前）；

since：语气较弱，表“已知、显而易见的原因”（译为“既然、因为”），常置于句首，主从句逻辑更偏向“因果顺承”；

as：语气最弱，表“伴随性、次要原因”（译为“由于”），常置于句首，主从句联系更松散，多用于书面语。

1. 由because引导的原因状语从句（强调直接原因）

1. She stayed at home yesterday because she had a bad cold.（她昨天待在家里，因为她得了重感冒。直接说明“待在家”的根本原因是“感冒”）

2. He didn’t attend the meeting because his car broke down on the way.（他没参加会议，因为他的车在路上抛锚了。）

3. I can’t help you with your homework because I have to finish my own report first.（我没法帮你写作业，因为我得先完成自己的报告。）

4. The sports meeting was canceled because the weather was too bad.（运动会取消了，因为天气太糟糕了。）

5. She cried because she couldn’t find her favorite toy.（她哭了，因为找不到她最喜欢的玩具了。）

6. We decided to take the train because the plane tickets were too expensive.（我们决定坐火车，因为机票太贵了。）

7. He was late for work because he forgot to set his alarm clock.（他上班迟到了，因为他忘了设闹钟。）

8. The cake tastes delicious because my mom added extra butter.（这蛋糕很好吃，因为我妈妈多放了黄油。）

9. I didn’t go to the party because I wasn’t invited.（我没去派对，因为我没被邀请。）

10. The river is dirty because some factories poured waste water into it.（这条河很脏，因为一些工厂往里面排废水。）

2. 由since引导的原因状语从句（表已知/显而易见的原因）

1. Since you know the truth, I don’t need to explain it again.（既然你已经知道真相了，我就不用再解释了。“你知道真相”是已知前提，据此得出“不用解释”的结论）

2. Since it’s raining heavily, we’d better stay indoors.（既然雨下得这么大，我们最好待在室内。“下雨”是显而易见的原因）

3. He didn’t buy the shirt since it was too small for him.（他没买那件衬衫，因为对他来说太小了。“尺寸不合适”是明确原因）

4. Since you’re free this weekend, why not come to my house for dinner?（既然你这周末有空，不如来我家吃晚饭吧？）

5. We walked to the park since it was only five minutes’ walk from our home.（我们步行去公园，因为从家到那儿只有五分钟路程。）

6. Since she’s good at English, she offered to help her classmates with their pronunciation.（既然她英语好，就主动帮同学练发音了。）

7. He didn’t watch the movie since he had already seen it twice.（他没看那部电影，因为他已经看过两次了。）

8. Since the store is closed today, we have to buy groceries tomorrow.（既然商店今天关门，我们只能明天买日用品了。）

9. She took an umbrella since the forecast said it would rain.（她带了伞，因为天气预报说会下雨。“天气预报”是已知依据）

10. Since you don’t like spicy food, I’ll order a mild dish for you.（既然你不喜欢吃辣，我就给你点个清淡的菜。）

3. 由as引导的原因状语从句（表次要/伴随性原因，书面语常用）

1. As the road was icy, the driver drove very slowly.（由于路面结冰，司机开得很慢。“路面结冰”是伴随性原因，语气较弱）

2. We had to wait for a while as the doctor was busy with another patient.（我们不得不等一会儿，因为医生正忙着看另一个病人。）

3. As she was afraid of the dark, she always sleeps with a small light on.（由于怕黑，她睡觉总是开着一盏小灯。）

4. He didn’t hear the phone ring as he was listening to music with headphones.（他没听到电话响，因为他戴着耳机听音乐。）

5. As the meeting was about to start, everyone hurried into the conference room.（由于会议快开始了，大家都匆匆走进会议室。）

6. The flowers died as nobody watered them while we were away.（花枯死了，因为我们不在的时候没人浇水。）

7. As he didn’t have enough money, he couldn’t buy the new laptop.（由于钱不够，他买不了那台新笔记本电脑。）

8. She spoke in a low voice as the baby was sleeping in the next room.（她说话声音很小，因为宝宝在隔壁房间睡觉。）

9. As the train was delayed, we arrived at our destination an hour late.（由于火车晚点，我们到达目的地时晚了一个小时。）

10. He didn’t join the outdoor activity as he had a lot of work to do.（由于有很多工作要做，他没参加户外活动。）

二、特殊引导词：for, now that, considering that（场景更具体）

这类引导词的用法场景更特殊，需注意与常用引导词的区别：

for：表“补充说明的原因”，不表直接原因，通常置于主句后，用逗号隔开，语气最弱（类似“毕竟、其实”）；

now that：表“既然（某事已发生）”，强调“当前情况已确定”，引导的原因多为“新出现的、已成立的事实”；

considering that：表“考虑到……（情况）”，引导的原因多为“需要兼顾的客观条件”，语气较正式。

1. 由for引导的原因状语从句（补充说明原因，置于句末）

1. He must be at home, for the lights in his room are on.（他一定在家，因为他房间的灯亮着。“灯亮”是补充说明的依据，而非直接原因——直接原因可能是“他说过今晚在家”，“灯亮”是佐证）

2. She is probably tired, for she has been working all day without a break.（她可能累了，毕竟她已经工作了一整天没休息。）

3. The ground is wet, for it rained last night.（地面是湿的，因为昨晚下过雨。“下雨”是补充说明“地面湿”的原因）

4. He didn’t want to go out, for he felt a little sick.（他不想出门，其实是因为有点不舒服。）

5. The book is worth reading, for it tells a lot of interesting historical stories.（这本书值得一读，因为它讲了很多有趣的历史故事。）

6. She must like painting, for her room is full of her own artworks.（她一定喜欢画画，因为她房间里满是自己的作品。）

7. The party was a success, for everyone had a great time.（派对很成功，毕竟大家都玩得很开心。）

8. He knows the city very well, for he lived here for ten years.（他对这座城市很熟悉，因为他在这里住过十年。）

9. The soup tastes good, for my grandma added a special herb to it.（这汤味道不错，因为我奶奶加了一种特别的调料。）

10. She didn’t answer the message, for her phone was dead.（她没回消息，因为她的手机没电了。）

2. 由now that引导的原因状语从句（表“既然某事已发生”）

1. Now that you’ve finished your exam, you can take a short trip to relax.（既然你已经考完试了，就可以去短途旅行放松一下。“考完试”是已发生的事实，据此建议“旅行”）

2. Now that the project is over, we can focus on the next task.（既然这个项目结束了，我们就可以专注于下一个任务了。）

3. He can speak French fluently now that he has studied it in Paris for a year.（既然他在巴黎学了一年法语，现在能说得很流利了。）

4. Now that you know how to use the software, you can finish the work alone.（既然你已经知道怎么用这个软件了，就可以自己完成工作了。）

5. We don’t need to buy more rice now that my mom brought a lot from her hometown.（既然我妈妈从老家带了很多米来，我们就不用再买了。）

6. Now that the weather is getting warm, we can start planting vegetables in the garden.（既然天气变暖和了，我们就可以在花园里种蔬菜了。）

7. She doesn’t need to take the bus now that her dad bought her a new bike.（既然她爸爸给她买了新自行车，她就不用坐公交了。）

8. Now that you’ve apologized, I won’t be angry with you anymore.（既然你已经道歉了，我就不再生气了。）

9. We can have a picnic in the park now that it’s not raining anymore.（既然雨停了，我们就可以去公园野餐了。）

10. Now that he has got his driver’s license, he can drive his parents to the supermarket.（既然他拿到驾照了，就可以开车送父母去超市了。）

3. 由considering that引导的原因状语从句（表“考虑到……情况”）

1. Considering that he is only a 5-year-old kid, he did a great job in the drawing competition.（考虑到他只是个5岁的孩子，他在绘画比赛中表现得已经很好了。“5岁”是需要兼顾的客观条件）

2. Considering that the hotel is near the airport, the price is quite reasonable.（考虑到这家酒店离机场很近，这个价格相当合理。）

3. She did well in the interview considering that she had no work experience before.（考虑到她之前没有工作经验，她在面试中表现得不错。）

4. Considering that it’s your first time cooking, the dish doesn’t taste bad.（考虑到这是你第一次做饭，这道菜味道不算差。）

5. We decided to postpone the trip considering that many of us are busy this month.（考虑到我们很多人这个月都忙，我们决定推迟旅行。）

6. Considering that the road is under construction, we’d better take an alternative route.（考虑到这条路正在施工，我们最好走另一条路线。）

7. He didn’t win the game but we still praised him considering that he tried his best.（他没赢比赛，但考虑到他已经尽力了，我们还是表扬了他。）

8. Considering that the book is written in simple English, it’s suitable for beginners.（考虑到这本书是用简单英语写的，很适合初学者。）

9. We didn’t blame her considering that she was not feeling well that day.（考虑到她那天身体不舒服，我们没有责怪她。）

10. Considering that the train ticket is cheaper and safer, I prefer to take the train instead of the plane.（考虑到火车票更便宜也更安全，我宁愿坐火车而不是飞机。）

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