1、用that引導

(1)當先行詞是人時，只用that

The people that lived here is a dentist.

(2)當先行詞是兩個或兩個以上的人或物，用that

(3)當先行詞是all,much,many,little,something,anything,eveything,nothing,none等詞時，只用that

(4)先行詞是系動詞be后邊的表語或關系代詞本身是從句中的表語時，用that

This is a song that will be popular soon.

(5)主句用there be句型開頭時，主語若指物，多用that

There is a position in the car that is still free.

(6)當先行詞是最高級形容詞或被最高級形容詞修飾時用that

(7)當先行詞被序數(shù)詞修飾時

The third university that we visited is Beijing University.

(8)當先行詞被very,only,one of,any,all,no,little,few等修飾時

(9)以who/which開頭的句子中為避免重復，用that.

2、只用which

(1)在限定性定語從句中，作介詞賓語提前時，只用which

This is the ship in which.......

(2)非限定性定語從句中，只指物。