宾语从句和定语从句是英语中常见的两种从句，但在语法和用法上有显著差异。宾语从句作为主句谓语动词的宾语，通常以连词开头，放在主句后，不用逗号隔开。定语从句用来修饰名词或代词，通常放在被修饰的名词或代词后，用关系词引导，与主句之间用逗号隔开。区分这两种从句的关键在于观察从句在句子中的作用。
什么是宾语从句
宾语从句是作为主句谓语动词的宾语的从句。它通常以连词that, if, whether, why, when, where, how等开头。宾语从句通常放在主句后面，并且不用逗号隔开。
例如：
- I know [that you are busy].
- She asked [if I was ready].
- He doesn't know [whether he should go or stay].
什么是定语从句
定语从句是用来修饰名词或代词的从句。它通常放在被修饰的名词或代词后面，并用关系词who, whom, whose, which, that等引导。定语从句和主句之间用逗号隔开。
例如：
- The girl [who is standing over there] is my sister.
- I bought the book [that you recommended to me].
- The car [which is parked outside] is mine.
区分宾语从句和定语从句
区分宾语从句和定语从句的方法是看从句在句子中的作用。如果从句是作为主句谓语动词的宾语，那么它就是宾语从句；如果从句是用来修饰名词或代词，那么它就是定语从句。
例如：
- I know [that you are busy]. (宾语从句)
- The girl [who is standing over there] is my sister. (定语从句)
- She asked [if I was ready]. (宾语从句)
- I bought the book [that you recommended to me]. (定语从句)
