本文目录
定语从句是英语中常用的修饰成分，用于对先行词进行进一步的说明和补充。在定语从句中，that是一个非常常见的引导词，但是在某些情况下，我们可以省略that，使句子更加简洁明了。
什么是定语从句？
定语从句是用来修饰名词或代词的从句，通常由关系代词who, whom, whose, that或者关系副词when, where引导，同时它与主句之间存在着一定的关系。定语从句可以为主语、宾语、表语或定语等。
例如：
- The boy who is standing there is my brother.
- The book that I borrowed from the library is very interesting.
定语从句中的that
在定语从句中，that通常被用来引导非限制性定语从句，比如：
- The book, which is on the table, is very interesting.
- The book that is on the table is very interesting.
这两个句子的意思是一样的，但是第二个句子中的that是可以省略的，也就是说，我们可以说：
- The book on the table is very interesting.
可以省略that的情况
除了上述的非限制性定语从句中，that还可以省略的情况包括：
- 定语从句中的谓语动词是be动词时，比如：
- The girl who is in the red dress is my sister.
- The girl in the red dress is my sister.
- 定语从句中的谓语动词是动词不定式时，比如：
- The book that I want to read is not available.
- The book I want to read is not available.
- 定语从句中的谓语动词是表示看、听、感觉等动词时，比如：
- The movie that I watched last night was very good.
- The movie I watched last night was very good.
省略that的注意事项
虽然我们可以省略定语从句中的that，但是需要注意以下几点：
- 当定语从句中的主语和主句的主语不一致时，不能省略that。比如：
- The man who is talking to your mother is my boss.
- The man that is talking to your mother is my boss. (不正确)
- 当定语从句中的关系代词后面有介词时，不能省略that。比如：
- The table on which the book is placed is very old.
- The table that the book is placed on is very old. (不正确)
- 当定语从句中有两个或以上的谓语动词时，只能省略最后一个that。比如：
- The book that I bought and that I read last night was very interesting.
- The book I bought and read last night was very interesting.
结论
定语从句是英语中非常重要的一种修饰成分，在写作和口语中都会经常用到。虽然that是定语从句中非常常见的引导词，但是在某些情况下，我们可以省略它，使句子更加简洁明了。但是需要注意的是，省略that时需要遵循一定的语法规则，否则会影响句子的准确性和通顺度。
