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English definition of “operation”

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operation

noun uk   /ˌɒp.ərˈeɪ.ʃən/ us    /ˌɑː.pəˈreɪ-/

operation noun (WORK)

C1 [U] the fact of operating or being active: There are several reactors of the type in operation (= working) at the moment. We expect the new system for assessing claims to come into operation (= start working) early next year. [U] the way that parts of a machine or system work together, or the process of making parts of a machine or system work togetherC1 [C] a business organization: Less profitable business operations will have difficulty in finding financial support.C1 [C] an activity that is planned to achieve something: a military/peacekeeping operation. Following the earthquake, a large-scale rescue operation was launched. [+ to infinitive] The operation to fly in supplies will begin as soon as possible.
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operation noun (MEDICAL PROCESS)

B1 [C] ( UK informal op) an occasion when a doctor cuts a body for medical reasons in order to repair, remove, or replace an unhealthy or damaged part: a major/minor/routine operation an abdominal/cataract/transplant operation He's got to have an operation on his shoulder. [+ to infinitive] We will know in a couple of days if the operation to restore her sight was successful.
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operation noun (MATHEMATICS)

[C] specialized mathematics a mathematical process, such as addition, in which one set of numbers is produced from another
(Definition of operation from the Cambridge Advanced Learners Dictionary & Thesaurus © Cambridge University Press)
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