一、关系代词用来引导定语从句。它代表先行词,同时在从句中作一定的句子成分。关系代词有主格,宾格和属格之分,并有指人与指物之分。关系代词有主格,宾格和属格之分,并有指人与指物之分。that的用法最广,that 可指人也可指物。例如:

限定性
指人 非限定性
指物 限定性
指人或指物
主 格 who/that which that
宾 格 whom which/that that
属 格 whose of which/whose of which/whose
1.The girl whom I spoke to is my cousin.
跟我讲话的姑娘是我表妹。
2.This is the pencil whose point is broken.
这就是那个折了尖的铅笔。
(whose 指物,在限定性定语从句中作定语)
3.He came back for the book which he had forgotten.
他重新回来都忘记了他的那本书。
(which指物,在限定性定语从句中作宾语,可以省略)
4.He said he saw me there, which was a lie.
他说在那儿看到了我,纯属谎言。

二、关系代词which的先行词可以是一个句子,例如:
1.He said he saw me there,which was a lie.

他说在那儿看到了我,纯属谎言。
2.Water, which is a clear liquid, has many uses.
水是一种清澈的液体,有许多用途。
3.I admired the patience with which she spoke.
她说话有极大的耐心,我很钦佩。

三、说明:关系代词that在从句中作宾语或表语时可省略, 例如:
1.I've forgotten much of the Latin I once knew
我过去懂拉丁语,现在大都忘了
2.He's changed. He's not the man he was.
他变化很大,已不是过去的他了