一、意思不同
1、that：用於某些動詞、形容詞和名詞後，引出從句，那，那個。
2、which：哪一個，哪一些，(明確所指的事物)…的那個。
1、that：that用作關係代詞時在下列情況下可以省略，引導限制性定語從句在從句中用作賓語時， 用在there be結構前作主語時，用作表語時，在定語從句與先行詞之間有插入語時。
2、which：which用作關係代詞，可引導限制性定語從句或非限制性定語從句，引導非限制性定語從句時which可以用整個主句作為其前行詞，相當於and that，有時還可引導不定式短語從句。
1、that：that可指人和物。
2、which：which則一般指物。
注意：先行詞為疑問詞who或which時，限制性定語從句的關係代詞只能用that引導。
1.當先行詞是nothing, something, anything, all, each等不定代詞時。
e.g. Do you have anything that is important to tell me?
2.當先行詞被all, any, some, no, not, every, each等修飾時。
e.g. I have some books that are very good.
3.當先行詞被形容詞最高階、序數詞所修飾時。
e.g. This is the first book that I bought myself.
The biggest bird that I caught is this bird.
4.主句是以which或who開頭的特殊疑問句時
e.g. Which is the bike that you lost?
Who is the woman that was praised at the meeting.
5.當先行詞在從句和主句中都作表語時,無論先行詞是人還是物.
China is no longer the country that she was.
6.如有兩個定語從句,其中一個已用which引導,另一個宜用that .
Edison built up a factory which produced things that had never been seen before.
7.在there be句型中,只用that.
He asked for the latest book (that) there is on the subject.
8.當先行詞被the very, the last, the next, the only 等詞修飾時。
e.g. This is the very book that I lost yesterday.
9.當先行詞又有人又有物時。
e.g. I won’t forget the things and the persons that I saw.
1、非限制性定語從句中。
e.g. Mary has a book, which is very precious.
2、在介詞之後。
e.g. This is a house in which lives an old man.
3、當主句中的主語被that修飾時。
e.g. That dog which I found in the street belongs to Mary.
定語從句（也稱關係從句、形容詞性從句），一個句子跟在一個名詞或代詞（先行詞）後進行修飾限定（對詞句進行補充、修飾、限定，進而使原句內容更完整），就叫做定語從句。按語法句式，定語從句在整個句子中做定語的成分 .被修飾的詞叫先行詞。定語從句不同於單詞作定語的情況，它通常只能放在被修飾的詞（即先行詞）之後。
定語從句由關係詞（關係代詞、關係副詞）引導，關係代詞、關係副詞位於定語從句句首。
一、意思不同
1、that：用於某些動詞、形容詞和名詞後，引出從句，那，那個。
2、which：哪一個，哪一些，(明確所指的事物)…的那個。
二、用法不同1、that：that用作關係代詞時在下列情況下可以省略，引導限制性定語從句在從句中用作賓語時， 用在there be結構前作主語時，用作表語時，在定語從句與先行詞之間有插入語時。
2、which：which用作關係代詞，可引導限制性定語從句或非限制性定語從句，引導非限制性定語從句時which可以用整個主句作為其前行詞，相當於and that，有時還可引導不定式短語從句。
三、側重點不同1、that：that可指人和物。
2、which：which則一般指物。
注意：先行詞為疑問詞who或which時，限制性定語從句的關係代詞只能用that引導。
使用that的情況：1.當先行詞是nothing, something, anything, all, each等不定代詞時。
e.g. Do you have anything that is important to tell me?
2.當先行詞被all, any, some, no, not, every, each等修飾時。
e.g. I have some books that are very good.
3.當先行詞被形容詞最高階、序數詞所修飾時。
e.g. This is the first book that I bought myself.
The biggest bird that I caught is this bird.
4.主句是以which或who開頭的特殊疑問句時
e.g. Which is the bike that you lost?
Who is the woman that was praised at the meeting.
5.當先行詞在從句和主句中都作表語時,無論先行詞是人還是物.
China is no longer the country that she was.
6.如有兩個定語從句,其中一個已用which引導,另一個宜用that .
Edison built up a factory which produced things that had never been seen before.
7.在there be句型中,只用that.
He asked for the latest book (that) there is on the subject.
8.當先行詞被the very, the last, the next, the only 等詞修飾時。
e.g. This is the very book that I lost yesterday.
9.當先行詞又有人又有物時。
e.g. I won’t forget the things and the persons that I saw.
只能使用which的情況。1、非限制性定語從句中。
e.g. Mary has a book, which is very precious.
2、在介詞之後。
e.g. This is a house in which lives an old man.
3、當主句中的主語被that修飾時。
e.g. That dog which I found in the street belongs to Mary.
擴充套件資料定語從句（也稱關係從句、形容詞性從句），一個句子跟在一個名詞或代詞（先行詞）後進行修飾限定（對詞句進行補充、修飾、限定，進而使原句內容更完整），就叫做定語從句。按語法句式，定語從句在整個句子中做定語的成分 .被修飾的詞叫先行詞。定語從句不同於單詞作定語的情況，它通常只能放在被修飾的詞（即先行詞）之後。
定語從句由關係詞（關係代詞、關係副詞）引導，關係代詞、關係副詞位於定語從句句首。