n.

1. 操作；运转[U]
   The operation of this machine is simple.

   这个机器的操作很简单。

2. 经营；营运[U]
   The operation of a railroad needs many men.

   铁路的营运需要很多人。

3. 作用；效力[U][C]
   The operation of natural law is constant.

   自然法则的作用是永恒的。

4. 活动；工作；事[C][P1]
   The rescue operation lasted three days.

   救援活动持续了三天。

5. 【医】手术[C][（+on/for）]
   Her father underwent a major operation last week.

   她父亲上周动了一次大手术。

6. 军事行动，作战[C][P1]
   The general was in command of operations in the north.

   将军负责指挥北方的作战行动。

7. 交易，买卖[C][P1]
   He continued his operations in cotton futures.

   他继续进行棉花期货交易。

8. 【数】运算[C]
9. （尤指法律文件的）生效[U]

n.

1. the action or process of operating.
2. an act of surgery performed on a patient.
3. an organized activity involving a number of people:
   a rescue operation.
4. a business organization; a company.
5. Mathematics  a process in which a number, quantity, expression, etc. is altered or manipulated according to set formal rules.