that常用作关系代词，可指代某人，也可指代某物，指物时有的时候可用which替换that，指人时可用who替换。但在下列情况下，一般用that。
一、that指代某物事时
1.先行词为all, few, little, much, the one, something, anything, everything, nothing等时。如：
2. 先行词被all, every, no, some, any, (a)few, (a)little, much等限定词修饰时。如：
3. 先行词被序数词或形容词最高级修饰时。如：
4. 先行词被the only, the very, the right, the last 等修饰时。如：
5. 先行词是并列结构，既有人又有物时。如：
6. 先行词前有the same 修饰，表示和先行词是同一物时。如：
注：如果表示的是与先行词同一类或相似的某物，则用the same…as….如：
7. 先行词为数词时。
8. 如果which引导的定语从句中又含有一个定语从句，为避免重复，第二个定语从句用that。如：
9. 以which作主语开头的特殊问句，为了避免重复，定语从句用that。如。
10. 关系代词在定语从句中作表语时，而且通常省略。如：
11. 关系代词在there be 句型中作主语时,而且常可以省略。如：
二、that 指代某人时。
1. 泛指某人时。如：
2. 主句是以作主语的who开头的特殊问句，为了避免重复时。如：
3. 先行词前有the same时。如：
4. 关系代词在定语从句中作表语时。如：
另外，that也可用作关系副词，表示时间、地点、原因和方式，在口语中可以用来代替when, where, why 引导的定语从句。在以下名词day, year, time, moment, reason, place等作先行词时，可用that 作关系副词引导定语从句。如：
（注：先行词是time,前面有序数词或last修饰时，常用that引导定语从句或者省略。）
当先行词为表示方式的词the way时，可用that引导定语从句, that常可以省略。
我不喜欢你和她说话那种方式。
只能用that
巧记定语从句只用that的情况
1. 当先行词是everything, anything, nothing , all, none, few, little, som，much等不定代词时，或当先行词受every, any, all, some, no, little, few, much等词修饰时。
2. 当先行词被序数词修饰时。
3. 当先行词被形容词最高级修饰时。
4. 当先行词被the very, the only, the first / last等修饰时。
5. 当先行词前面有who, which等疑问代词时。
6. 当先行词为人与动物或人与物时。如：
Look at the man and his donkey that are walking up the street.
7. 当先行词是reason, way（方法）等词时，关系代词常用that代替in which, for which, why, 也常可省略
8. 先行词前有the same 修饰，表示和先行词是同一人或者物时。
注：如果表示的是与先行词同一类或相似的某物，则用the same…as….
9. 关系代词在there be 句型中作主语时,而且常可以省略。
巩固练习：
1. This is the same book______ I lost the other day. There's my name on it.
A. that
B. as
C. /
D. which
2. I hope that the little _______ I have been able to do does good to them all.
A. which
B. what
C. that
D. when
3. The first place ______ the children were taken to see was their workshop.
A. that
B. which
C. what
D. where
4. Tell me everything _________ you know.
A. which
B. about that
C. about which
D. that
5. This is the biggest library ______ I have ever seen.
A. which
B. what
C. where
D. that
6. This is the very person _______I am looking for.
A. which
B. that
C. who
D. whom
7. What surprised me was not what he said but _________ he said it.
A．the way B．in the way that
C．in the way D．the way which
8. This is all ________ I can do for you.
A. which
B. what
C. it
D. /
9. The book doesn't say much _______ amuses children.
A. what
B. that
C. whose
D. to which
10. There is nothing about him ________ I know of.
A. that
B. which
C. whom
D. who
