关系代词which的用法，如果先行词是事物或动物，该用什么呢?也用who, whose, whom吗?代替人的是人称代词，代替事物或动物的是指示代词。
同样的，也单有代替事物或动物的关系代词，并且也分为主格、所有格和宾格。
来看几个例句。
This is thebook. 这是本书。
It is very interesting. 它非常有趣。
把这两个句子合成一个简练的句子。
This is thebookit is very interesting. (×)
→ 不能直接将两个句子首尾相连。
This is the bookandit is very interesting. (√)
→ 句子正确，但是不够简练。
This is the bookwho is very interesting. (×)
→ who只能用于先行词是人的时候。
This is the bookwhich is very interesting. (√)
这是一本非常有趣的书。
→ 先行词是事物时，应该用关系代词which。
先行词是事物或动物时，用which代替who。
√ 先行词是事物或动物时，关系代词也分为主格、所有格和宾格。
1. 主格关系代词
无论先行词是人还是物，关系代词的原理都是一样的。关系代词引导修饰名词的定语从句，同时起连词和代词的作用。因此关系代词要根据原来句子中代词的性质进行选择。
一起来看几个先行词是事物或动物的例句。
(1)先行词是事物
This is theletter. 这是那封信。
It arrived yesterday. 它昨天到的。
This is the letter it arrived yesterday. (×)
This is the letter andit arrived yesterday. (√)
This is the letter which arrived yesterday. (√)
这是昨天到的那封信。
(2)先行词是动物
I like thecat. 我喜欢那只猫。
It has blue eyes. 它有蓝色的眼睛。
I like the cat it has blue eyes. (×)
I like the cat andit has blue eyes. (√)
I like the cat which has blue eyes. (√)
我喜欢那只有蓝色眼睛的猫。
√ 先行词是人时，人称代词是主格形式就用who，先行词是事物或动物时，人称代词是主格形式就用which。
2. 所有格关系代词
事物或动物的所有格和人的所有格是一样的，都用whose。下面来看例句。
(1)先行词是事物
This is thetable. 这是那张桌子。
Its leg was broken yesterday. 它的桌腿昨天坏了。
This is the table its leg was broken yesterday. (×)
This is the table andits leg was broken yesterday. (√)
This is the table whose leg was broken yesterday. (√)
这是昨天桌腿坏了的那张桌子。
(2)先行词是动物
I love thecat. 我喜欢那只猫。
Its hair is black. 它的毛是黑色的。
I love the cat its hair is black. (×)
I love the cat andits hair is black. (√)
I love the cat whose hair is black. (√)
我喜欢那只毛是黑色的猫。
无论是人，还是事物、动物，所有格关系代词都可以用whose。另外，先行词是事物时，也可以用of which代替whose。
所以，事物的所有格关系代词既可以用whose，也可以用ofwhich。
3. 宾格关系代词
先行词是人时，宾格关系代词用whom;先行词是事物或动物时，宾格关系代词用which。
This is thecar. 这是那辆小汽车。
I bought it yesterday.我昨天买的。
将这两个句子合在一起。
This is the car I bought it yesterday. (×)
This is the car and I bought it yesterday. (√)
This is the car I bought which yesterday. (×)
This is the car which I bought yesterday. (√)
这是我昨天买的小汽车。
√ 原来句子中的宾语在后面，但是在定语从句中用关系代词代替时一定要移至前面。
一起看下面的例句。
I know thesong. 我知道这首歌。
You like it. 你喜欢它。
I know the song you like it. (×)
I know the song and you like it. (√)
I know the song you like which. (×)
I know the song which you like. (√)
我知道你喜欢的那首歌。
Thefish is still alive. 那条鱼还活着。
I caught it yesterday. 我昨天抓到的。
The fish is still alive I caught it yesterday. (×)
The fish is still alive and I caught it yesterday. (√)
The fish is still alive which I caught yesterday. (√)
→ 这个句子是正确的，但是定语从句(which I caught yesterday)与先行词(the fish)距离太远了，容易混淆。
The fish which I caught yesterday is still alive. (√)
我昨天抓到的那条鱼还活着。
→ 定语从句紧跟在先行词后，句子的意思会更明确。
√ 在使用宾格关系代词的句子中，为了让句子的意思更明确，定语从句最好紧跟着先行词。
