| 类型 § | if 条件从句时态 | 主句时态 |
|---|---|---|
| 真实条件 (Real Condition) | 一般现在时 | 一般现在时 / 将来时 |
| 将来可能实现的条件 | 一般将来时 (will + 动词原形) | |
| 与现在/将来相反的虚拟条件 (Unreal Condition) | 一般过去时 (be 动词多用 were) | would / could / should / might + 动词原形 |
| 与过去相反的虚拟条件 | 过去完成时 (had + 过去分词) | would / could / should / might + have + 过去分词 |
- 真实条件 (可能实现的) If it rains, I will take an umbrella. 如果下雨，我会带伞。
- 将来可能实现的条件 If it is sunny tomorrow, we will go for a picnic. 如果明天晴朗，我们会去野餐。
- 与现在/将来相反的虚拟条件 (不可能实现的) If I were a bird, I would fly in the sky. 如果我是一只鸟，我就会在天空中飞翔。
- 与过去相反的虚拟条件 If I had studied harder, I would have passed the exam. 如果我当时学习更努力些，我就会通过考试了。