【关于定语从句中只用that的七种情况】在英语学习中，定语从句是一个重要的语法知识点，尤其在使用关系代词时，常常会遇到“which”和“that”的选择问题。虽然在大多数情况下，“which”和“that”可以互换使用，但在某些特定语境下，只能使用“that”，而不能使用“which”。本文将总结出定语从句中只用that的七种常见情况，帮助学习者更准确地掌握这一语法点。
一、定语从句中先行词是不定代词
当先行词是all, everything, something, nothing, anything, little, much等不定代词时，通常只用“that”。
| 先行词 | 关系代词 | 例句 |
| everything | that | I told you everything that happened. |
| something | that | There is something that I need to tell you. |
二、先行词前有最高级或序数词修饰
如果先行词被最高级或序数词（如first, second, third）修饰，则必须使用“that”。
| 先行词 | 关系代词 | 例句 |
| the best movie | that | This is the best movie that I have ever seen. |
| the first day | that | That was the first day that I met her. |
三、先行词是the only + 名词
当先行词为the only加名词时，必须用“that”。
| 先行词 | 关系代词 | 例句 |
| the only person | that | She is the only person that can help us. |
| the only way | that | This is the only way that we can solve the problem. |
四、先行词是one of + 复数名词
在“one of + 复数名词”结构中，关系代词只能用“that”。
| 先行词 | 关系代词 | 例句 |
| one of the students | that | He is one of the students that passed the exam. |
| one of the books | that | This is one of the books that I read last year. |
五、先行词是the same... as结构中的名词
在“the same... as”结构中，若先行词是名词，且后面接的是一个完整的从句，应使用“that”。
| 先行词 | 关系代词 | 例句 |
| the same book | that | This is the same book that I read yesterday. |
| the same man | that | He is the same man that helped me before. |
六、先行词是whoever, whatever, whichever等疑问代词
当先行词是whoever, whatever, whichever等疑问代词时，只能用“that”。
| 先行词 | 关系代词 | 例句 |
| whoever | that | Give it to whoever that comes first. |
| whatever | that | Do whatever that you want. |
七、先行词是all或the one等强调性表达
当先行词是all、the one、the one and only等强调性表达时，也应使用“that”。
| 先行词 | 关系代词 | 例句 |
| all | that | All that glitters is not gold. |
| the one | that | He is the one that I was waiting for. |
总结表格
| 情况 | 先行词示例 | 关系代词 | 说明 |
| 不定代词 | everything, something, nothing | that | 必须用that |
| 最高级/序数词 | the best, the first | that | 必须用that |
| the only + 名词 | the only person, the only way | that | 必须用that |
| one of + 复数名词 | one of the students, one of the books | that | 必须用that |
| the same... as | the same book, the same man | that | 必须用that |
| whoever, whatever | whoever, whatever | that | 必须用that |
| all, the one | all, the one | that | 必须用that |
通过以上七种情况的总结，我们可以更加清晰地理解在定语从句中为何只能使用that。掌握这些规则，有助于提高英语写作和口语表达的准确性与地道性。希望本文对你的英语学习有所帮助！
