my,your,her,his是形容词性物主代词,剩下的是名词性物主代词。名词性物主代词=形容词性物主代词+名词。比如This is my book=This book is mine.如果前边已经提过book,就可以直接说It os mine.
Whose book is it?
It is mine=It is my book
my 是形容词性物主代词,表示“我的XX”,后面需要加名词XX,例如 This is my book(这是我的书)
mine是名词形物主代词,特指“我的某某东西”,它本身就可做名词,例如This book is mine(这本书是我的)
your-yours,her-hers,his-his(这个不变),都是一样的道理