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operation

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noun American English pronunciation: operation /ˌɑpəˈreɪʃ(ə)n/ 
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singularoperation
pluraloperations
  1. 1
    [countable] a planned activity involving a lot of people, especially soldiers or police officers

    This was the biggest military operation in 20 years.

    Undercover operations led to the arrest of the gang.

    rescue/relief/cleanup operation:

    The cleanup operation will take weeks.

  2. 2
    [countable] an action or set of actions that is necessary to achieve something

    Connecting the water supply is a very simple operation.

    The computer performs this operation many times every day.

  3. 3
    [countable] the process of cutting into someone's body for medical reasons

    a stomach/heart operation

    have/undergo an operation:

    The baby had to have an operation, but he's fine now.

    operation on:

    She may need an operation on her knee.

    do/perform/carry out an operation:

    A very experienced heart surgeon will perform the operation.

  4. 4
    [uncountable] the way that something such as a system or service operates

    We are visiting schools to explain the operation of the new exam system.

    1. a.
      used about the way that a machine or piece of equipment operates

      Something was interfering with the radar equipment's operation.

    2. b.
  5. 5
    [countable] a company, or a part of a large company

    The company has recently expanded its international operation.

    The group is selling its overseas operations.

  6. 6
    [uncountable] the process of controlling something or of making it work

    Operation of this equipment requires special training.

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