限定性定语从句和非限定性定语从句的比较

在讨论定语从句时从先行词与定语从句的角度看来，有限定性和非限定性定语从句两种情况。详解如下。
1.限定性定语从句
限定性定语从句在句中的主要作用是修饰前面的先行词，并且两者之间紧密联系，无逗号。如出现关系代词是that的情况，that是可以省略的。在句中起修饰限定作用，不能不省去。

A.The sports meeting will be held tomorrow when all the things are prepared.

明天所有的事情都准备就绪时，便会举行运动会。（限定性）

B.We think about the final exam which (that)will become a standard of scores in the semester.

我们都在想着这学期将会作为评分标准的期末考试。（that可以省略）

A.what a terrible thing！Mary missed the last bus, which let her late for the class.

太糟糕了！玛丽错过了最后一班公交，使得她上课迟到。

B.My cousin failed the examination, which made her pretty sad.

我表妹考试失利的事让她非常难过

A.My friend told me she had a nightmare, which scared her a lot.

我朋友告诉我说，她做了一个令她害怕的恶梦。