引導定語從句的關係詞有關係代詞和關係副詞,常見的關係代詞包括that,which,who，那麼，定語從句that用法是？
(1)不用that的情況
(a) 在引導非限定性定語從句時。
(錯)The tree, that is four hundred years old, Is very famous here.
(b) 介詞後不能用。
We depend on the land from which we get our food.
We depend on the land that/which we get our food from.
(2) 只能用that作為定語從句的關係代詞的情況
(a) 在there be 句型中，只用that，不用which。
(b) 在不定代詞，如：anything, nothing, the one, all等作先行詞時，只用that，不用which。
(c) 先行詞有the only, the very,the same,the last,just修飾時，只用that。
(d) 先行詞為序數詞、數詞、形容詞最高階時，只用that,不能用which。.
(e) 先行詞既有人，又有物時。
(f) 先行詞指物，在主句中作表語時.
(g) 為了避免重複.
(h)先行詞是the way或the reason時，that可作關係副詞，也可省略
(i) 主句的.主語是疑問詞who /which時
定語從句that例句
1. He is a good boy. 形容詞作定語
2. Two boys need two pens. 數詞作定語
3. His son needs Tom's pen. 形容詞性物主代詞或名詞所有格作定語
4. The boy in blue is Tom. 介詞短語作定語
e is a woman doctor. 名詞作定語
6. The boy there needs a bike. 副詞作定語
e is nothing to do today. 不定式作定語
8. The smiling boy needs a friend. 現在分詞作定語
9. A boy called Tom saved the girl. 過去分詞(短語)作定語
10. He is the man that I met yesterday. 定語從句
定語從句知識
一、定語從句的概念：在複合句中，用作定語的從句叫做定語從句。
二、定語從句的位置：通常位於它所修飾的名詞或代詞之後。
三、被修飾的名詞或代詞叫做先行詞。
四、引導定語從句的關聯詞為關係代詞和關係副詞。關係代詞(who, whom, whose, that, which等)在定語從句中可用作主語、定語、賓語等;關係副詞(when, where, why等)在定語從句中只用作狀語。關係代詞和關係副詞放在先行詞及定語從句之間起連線作用，同時又作定語從句的重要成分。
五、定從基本形式：先行詞(名詞/代詞) + 關係代詞/關係副詞+ 定從
六、that引導的定語從句
She is the girl that talked to you yesterday. (that作主語)
The coat (that) I put on the desk is blue. (that作賓語)
結論：that引導的定語從句既可以修飾人，也可以修飾物;
that在從句中作主語或賓語;
作主語時不可省略，作賓語可省略。
例如：
1. I like music. I can dance to music.
I like music that I can dance to. (that在從句中用作賓語。)
2. I prefer a sandwich. A sandwich is really delicious.
I prefer a sandwich that is really delicious.(that在從句中用作主語。)
注意：that在定語從句中作主語時，定語從句中謂語動詞的單複數應與先行詞保持一致.
例如：I prefer movies that are scary.
I like a sandwich that is really delicious.
I love the singer that is beautiful.
I have a friend that plays sports.
