by
1.catch him by the ear, lead her by the hand等表达方式里的the照习惯不可改作his或her。
2.下面两句意思相同：
- Books came in by the hundred.
- Books came in by hundreds.
注意不可说by the hundreds。
They are paid by the month和Sugar is sold by the catty等句子里的by the month和by the catty等不可改作by months和by catties等。
3.by and by作“不久以后”解，不作“渐渐地”解。
