定语从句是雅思写作的常用句型，在雅思写作中起到了各种修饰和限制的作用。但是其实大部分同学对其用法模糊，不够细致和确定，所以使得考生容易掉以轻心，在雅思写作的应用中出错，得不偿失。
“常用that 不用which”是定语从句的基本用法。
1.当先行词为all， little， much， few， everything， none 等不定代词时关系代词用that而不用which.
I will tell him all that you told me at the ball.
There are few books that you can read in this book store.
2.当先行词既有人又有物时，关系代词用that， 不用which.
He asked about the factories and workers that he had visited.
3.当先行词有形容词最高级修饰时，关系代词用that， 而不用which.
This is the best novel that I have ever read.
Guilin is one of the most beautiful cities that I have ever visited.
4.当先行词有序数词修饰时，关系代词用that， 不用which.
The first sight that was caught at the Great Wall has made a lasting impression on him.
5.当先行词被the only， the very， the same， the right等修饰时，关系代词用that，不用which.
That is the very thing that we can do.
It is the only book that he bought himself.
6.当先行词被all， every， any， much， little， few， no等修饰时，关系代词用that，不用which.
You can take any room that you like.
There is no clothes that fit you here.
7.当主句是以which开头的特殊问句时，定语从句关系代词一般用that而不用which.
Which of the books that had pictures was worth reading?
8.在强调句型" It is ... that ..." 中，只用that，不用which.
It is in this room that he was born twenty years ago.
