定语从句和分词作定语之间的转化

1. 基本规则：在有定语从句的复合句中，如果定语从句中先行词是从句的主语（也即关系代词作从句的主语），则这个定语从句可以转化为以过去分词或现在分词作定语的形式。同样的，分词作定语也可以转化为一个定语从句。

2. 举例:There is a boy who is sleeping.   There is a sleeping boy.

        A teacher named Tom will teach us physics.   A teacher who is named Tom will teach us physics.(其实我们更常说A teacher whose name is…，但这种写法从语法上讲并没有错，所以也可以使用)

3. 语序：分词作定语置于名词之前，分词短语则应置于名词之后。

4. 总结：定语从句转化为分词作定语时，对于从句中的谓语动词用主动语态的，使用现在分词作定语；用被动语态的，使用过去分词作定语；用完成时态的，使用having+过去分词作定语。分词作定语转化为定语从句时，having+过去分词作定语转化为完成时态；过去分词作定语转化为被动语态；现在分词作定语转化为主动语态；具体时态酌情而定。

5. 举例：The boy who is going out forgot to put on his coat.   The boy going out forgot to put on his coat.

There are three doors which were locked.   There are three locked doors.

The teacher who had finished his class slowly went out.   The teacher having finished his class slowly went out.

The boy going out forgot to put on his coat.   The boy who is going/went out forgot to put on his coat.

There are three locked doors.   There are three doors which were/are locked.

he teacher having finished his class slowly went out.   The teacher who had finished his class slowly went out.

6. 特殊情况：对于表状态的不及物动词的过去分词作定语，转化为定语从句应用完成时态。

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