Learner's definition of OPERATION
1 [count] : a process in which a doctor cuts into someone's body in order to repair or remove a damaged or diseased part
She is recovering from a major heart operation. [=she is recovering from major heart surgery]
a minor/routine operation
organ transplant operations
2 a : a usually small business or organization b : an activity of a business or organization— usually plural 3 [noncount] : the state of functioning or being used— used with in or into
The system is now in operation.
The mill has been in operation for over 100 years.
Safety goggles must be worn while the machine is in operation. [=in use]
The dam will go into operation next month.
4 [noncount] : the way something functions or is used 5 [count] : a set of planned actions for a particular purpose
The city has launched an operation to clean up the neighborhood.
Ten arrests were made in an undercover operation.
a rescue operation
The military operation gave them control of the city.
6 [count] : a single action performed by a computer 7 [noncount] : the act of using and controlling something 8 [count], mathematics : a mathematical process (such as addition or multiplication) that is used for getting one number or set of numbers from others according to a rule