1、用做定語的從句叫做定語從句，一般修飾名詞或代詞。被修飾的名詞或代詞，我們稱之為先行詞，定語從句放在先行詞后。定語從句可以分為限制性定語從句和非限制性
定語從句。
⑴ 做賓語的關系代詞常可以省略；
⑵ 關系代詞在定語從句中做主語時，從句謂語動詞的數要和先行詞一致；
⑶ 先行詞為不定代詞 all、something、nothing、anything、little等不定代詞時或是序數詞或是形容詞最高級時，關系代詞用that 來引導，強調句中也可用that,
have you anything that you need?
the first thing第一件事情that we should do is to clean打算 the room.
it was the largest map that i ever曾經 saw.
it was liberation 解放that brought about 引起帶來a complete 徹底的change改變in his life.
⑷ 關系代詞在定語從句中亦可用作介詞的賓語，如: whom (指人)、which (指物)
this is the book for which you asked. 尋找
the person from whom the message came來自 did not say his name.
4、非限定性從句。
如果缺少了不會影響全句的主要思想，前面一般有逗號，翻譯時常譯成兩個句子，that和why一般不用于非限定性定語從句，也不能省略任何關系副詞。
sunday星期日 is a holiday假期, when people do not go to work.
i picked up撿起，拾起 the apples, some of which are badly bruised.碰傷