I want to know the difference of mouse and rats

Mouse is smaller and with a shorter tail. Rat is the type which you see on the dirty back street, which are generally dirtier, bigger and with more diseases. There are certain numbers of people around Europe keep rats as pets for curious reasons though. Rat pretty much eat everything human does, while mouse eats similar food as hamsters.

mouse係1隻老鼠(單數)
rats係幾隻老鼠(眾數)