Op`er*a"tion (?), n. [L. operatio: cf. F. opération.] 1. The act or process of operating; agency; the exertion of power, physical, mechanical, or moral.

The pain and sickness caused by manna are the effects of its operation on the stomach.

Speculative painting, without the assistance of manual operation, can never attain to perfection.

2. The method of working; mode of action.

3. That which is operated or accomplished; an effect brought about in accordance with a definite plan; as, military or naval operations.

4. Effect produced; influence. [Obs.]

The bards . . . had great operation on the vulgar.

5. (Math.) Something to be done; some transformation to be made upon quantities, the transformation being indicated either by rules or symbols.

6. (Surg.) Any methodical action of the hand, or of the hand with instruments, on the human body, to produce a curative or remedial effect, as in amputation, etc.

• the method by which a device performs its function. (It is dangerous to look at the beam of a laser while it is in operation.)
  
• the method or practice by which actions are done. (We run our operation from a storefront.)
  
• (Medicine) a surgical procedure. (She had an operation to remove her appendix.)
  
• (Mathematics) a procedure for generating a value from one or more other values (the operands; the value for any particular operands is unique)
  
• (Military) a military campaign (w:Operation Desert Storm)