【定语从句只用that的几种情况】在英语语法中，定语从句是用于修饰名词或代词的一种从句结构。在使用关系代词时，通常可以使用“which”、“that”、“who”、“whom”等。但有些情况下，只能使用“that”，而不能使用其他关系代词。掌握这些特殊情况，有助于更准确地运用定语从句。
以下是定语从句中只用that的几种常见情况：
一、当先行词是不定代词时
当先行词是“all”、“everything”、“nothing”、“something”、“anything”、“little”、“much”等不定代词时，只能用“that”。
| 先行词 | 关系代词 | 例句 |
| everything | that | I told you everything that happened. |
| nothing | that | There is nothing that can stop me. |
二、当先行词是最高级或序数词时
如果先行词是形容词最高级（如“the best”）或序数词（如“the first”），则只能用“that”。
| 先行词 | 关系代词 | 例句 |
| the best | that | This is the best movie that I have ever seen. |
| the first | that | She was the first person that called me. |
三、当先行词被“the only”修饰时
如果先行词前有“the only”，则只能使用“that”。
| 先行词 | 关系代词 | 例句 |
| the only one | that | He is the only person that knows the truth. |
四、当先行词是“the same”时
当先行词是“the same”时，关系代词必须用“that”。
| 先行词 | 关系代词 | 例句 |
| the same | that | This is the same book that I read last year. |
五、当先行词是“all”时
虽然“all”也可以出现在第一种情况中，但在某些特定语境下，尤其是强调整体时，也常用“that”。
| 先行词 | 关系代词 | 例句 |
| all | that | All that glitters is not gold. |
六、当从句中已有疑问词时
如果从句中已经含有疑问词（如“who”、“what”、“which”等），那么关系代词只能用“that”。
| 先行词 | 关系代词 | 例句 |
| the man | that | The man that I met yesterday is my teacher. |
七、当先行词是“the one”时
“the one”作为先行词时，通常只用“that”。
| 先行词 | 关系代词 | 例句 |
| the one | that | She is the one that I love. |
总结表格
| 情况说明 | 先行词示例 | 只能用的关系代词 |
| 不定代词 | everything, nothing, something | that |
| 最高级或序数词 | the best, the first | that |
| 被“the only”修饰 | the only one | that |
| “the same” | the same | that |
| “all” | all | that |
| 从句含疑问词 | the man, the book | that |
| “the one” | the one | that |
通过掌握这些“只用that”的情况，可以帮助我们在写作和口语中更自然、更准确地使用定语从句，避免常见的语法错误。