[ op-uh-rey-shuhn ]
See synonyms for: operationoperations on Thesaurus.com

  1. an act or instance, process, or manner of functioning or operating.

  2. the state of being operative (usually preceded by in or into): a rule no longer in operation.

  1. the power to act; efficacy, influence, or force.

  2. the exertion of force, power, or influence; agency: the operation of alcohol on the mind.

  3. a process of a practical or mechanical nature in some form of work or production: a delicate operation in watchmaking.

  4. a course or procedure of productive or industrial activity: building operations.

  5. a particular process or course: mental operations.

  6. a business transaction, especially one of a speculative nature; deal: a shady operation.

  7. a business, especially one run on a large scale: a multinational operation.

  8. Surgery. a procedure aimed at restoring or improving the health of a patient, as by correcting a malformation, removing diseased parts, implanting new parts, etc.

  9. Mathematics.

    • a mathematical process, as addition, multiplication, or differentiation.

    • the action of applying a mathematical process to a quantity or quantities.

  10. Computers. any discrete activity or action that is performed by a computer, as reading, writing, processing, sending, or receiving data: The http request operation has timed out.

  11. Military.

    • a campaign, mission, maneuver, or action.

    • Usually operations . the conduct of a campaign, mission, etc.

    • operations, a headquarters, office, or place from which a military campaign, air traffic to and from an airfield, or any of various other activities, is planned, conducted, and controlled.

    • operations, the people who work at such a headquarters.

Origin of operation

First recorded in 1350–1400; Middle English operacioun, oparacion, operation, from Latin operātiōn- (stem of operātiō ), equivalent to operāt(us) + -iōn- noun suffix of action or condition; see origin at operate

Other words from operation

  • mis·op·er·a·tion, noun
  • pre·op·er·a·tion, noun
  • re·op·er·a·tion, noun
  • sub·op·er·a·tion, noun

Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2023

British Dictionary definitions for operation


/ (ˌɒpəˈreɪʃən) /

  1. the act, process, or manner of operating

  2. the state of being in effect, in action, or operative (esp in the phrases in or into operation)

  1. a process, method, or series of acts, esp of a practical or mechanical nature

  2. surgery any manipulation of the body or one of its organs or parts to repair damage, arrest the progress of a disease, remove foreign matter, etc

    • a military or naval action, such as a campaign, manoeuvre, etc

    • (capital and prenominal when part of a name): Operation Crossbow

  3. maths

    • any procedure, such as addition, multiplication, involution, or differentiation, in which one or more numbers or quantities are operated upon according to specific rules

    • a function from a set onto itself

  4. a commercial or financial transaction

Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Scientific definitions for operation


[ ŏp′ə-rāshən ]

  1. Medicine A surgical procedure for remedying an injury, ailment, defect, or dysfunction.

  2. Mathematics A process or action, such as addition, substitution, transposition, or differentiation, performed in a specified sequence and in accordance with specific rules.

  1. A logical operation.

  2. Computer Science An action resulting from a single instruction.

The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.