1)、定义：人称代词是用来指代人、动物或事物的代词。它必须在人称(第一人称、第二人称、及第三人称)、数（单数、复数）以及性（阴性、阳性、中性）三方面与被指代的名词一致。
如：I am a student.
Tom is a boy, and he is a student.
Mary is very pretty, and she likes singing.
The boys are students, and they are in the room.
The doy is small. It is Tom's.
2、人称代词的句法功能
A) 人称代词有主格和宾语之分：主格用作主语，宾格用作宾语。
B) 人称代词的主格形式在在句中作主语和表语。
如: I like music(主语).
She is a teacher.(主语)
She and I are good friends(主语).
Neither she nor I am student.
——I saw the boys this morning.
——Are you sure it was they(表语)?
C) 人称代词的宾格在句子作动词的宾语，或者介词的'宾语。
如：I saw him at the party(宾语).
I haven't seen them recently. (宾语)
I bought a book for them. (作介词宾语)
=I bought them a book. (间接宾语)
【注意】
a. 在口语中，人称代词的主格形式作表语时，常常可以用宾格替换。
如：It can't be he/him.
——Is this Mr. Green?
——Yes, this is he/him.
b. 在口语中，当人称代词用于than, as 之后或用于强调句中被强调时，用主格(较正式)和宾格(较口语化)均可以。
如：
He sings better than I/me. 他比我唱得好。
You know more than she/her.
She is as tall as me(I am).
c. 单独使用的人称代词通常用宾格，即使它充当的是主语也是如此。如：
“I like English.”
“我喜欢英语。”
“Me too=I like English too.”
“我也喜欢。”