I、you、he、she、it。人称代词在句中作不同成分时有不同的形式，如：主格、宾格、第三人称单数形式等。
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
