her 形容词性物主代词,hers名词性物主代词，she在开头用,her是东西的主人,hers是连主人带东西。she is a girl。她是女孩 this is her book。这是她的书 this is hers。这是她的，hers后，不能加东西。
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 boy 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)?
It might have been she.
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)
