【关于定语从句中只用that的七种情况】在英语学习过程中，定语从句是一个重要的语法点。在使用关系代词时，通常“which”和“that”都可以引导定语从句，但在某些特定情况下，只能使用“that”，而不能使用“which”。为了帮助学习者更好地掌握这一规则，本文总结了定语从句中只用that的七种常见情况，并以表格形式清晰呈现。
一、
1. 当先行词是不定代词时：如 everything, anything, nothing, something 等。
2. 当先行词是最高级或序数词时：如 the first, the best, the most important 等。
3. 当先行词被形容词最高级修饰时：如 the most difficult problem。
4. 当先行词是人和物的混合时：即从句中同时指人和物，这时只能用 that。
5. 当关系代词在从句中作宾语且前面有介词时：此时不能用 which，而要用 that。
6. 当先行词是整个句子时：即用 that 引导一个完整的句子作为先行词。
7. 当从句中出现“all, the one, the only, the same”等限定性词语时：这些词后一般用 that。
二、表格展示
| 情况 | 先行词类型 | 示例 | 备注 |
| 1 | 不定代词 | Everything that he said was true. | 不能用 which |
| 2 | 最高级 / 序数词 | The first book that I read was interesting. | 如 the best, the last 等 |
| 3 | 被最高级修饰的名词 | The most important thing that happened was his arrival. | 不能用 which |
| 4 | 人和物混合 | The man and the dog that were in the picture are my uncle and my pet. | 只能用 that |
| 5 | 带有介词的宾语 | The person to whom I spoke was very polite.（错误） The person that I spoke to was very polite.（正确） | 介词后不能用 which |
| 6 | 整个句子作先行词 | That he failed the exam surprised everyone. | 不能用 which |
| 7 | 特定限定词后 | All that I need is time. The only thing that matters is your health. | 如 all, the only, the same 等 |
三、注意事项
- 在非限制性定语从句中，只能用 which，不能用 that。
- 在口语中，有时人们会混用 which 和 that，但正式写作中应严格区分。
- 掌握这些规则有助于提高英语表达的准确性和地道性。
通过以上内容的学习与练习，可以更清晰地理解在哪些情况下必须使用 that 来引导定语从句，从而避免常见的语法错误。希望这篇文章对你的英语学习有所帮助！