[op-uh-rey-shuh n]
See more synonyms for operation 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.
  3. the power to act; efficacy, influence, or force.
  4. the exertion of force, power, or influence; agency: the operation of alcohol on the mind.
  5. a process of a practical or mechanical nature in some form of work or production: a delicate operation in watchmaking.
  6. a course or procedure of productive or industrial activity: building operations.
  7. a particular process or course: mental operations.
  8. a business transaction, especially one of a speculative nature; deal: a shady operation.
  9. a business, especially one run on a large scale: a multinational operation.
  10. 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.
  11. Mathematics.
    1. a mathematical process, as addition, multiplication, or differentiation.
    2. the action of applying a mathematical process to a quantity or quantities.
  12. Military.
    1. a campaign, mission, maneuver, or action.
    2. Usually operations.the conduct of a campaign, mission, etc.
    3. 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.
    4. operations,the people who work at such a headquarters.

Origin of operation

1350–1400; Middle English operacioun < Latin operātiōn- (stem of operātiō), equivalent to operāt(us) (see operate) + -iōn- -ion
Related formsmis·op·er·a·tion, nounpre·op·er·a·tion, nounre·op·er·a·tion, nounsub·op·er·a·tion, noun
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018

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British Dictionary definitions for operation


  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)
  3. a process, method, or series of acts, esp of a practical or mechanical nature
  4. 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
    1. a military or naval action, such as a campaign, manoeuvre, etc
    2. (capital and prenominal when part of a name)Operation Crossbow
  5. maths
    1. any procedure, such as addition, multiplication, involution, or differentiation, in which one or more numbers or quantities are operated upon according to specific rules
    2. a function from a set onto itself
  6. 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

Word Origin and History for operation

late 14c., "action, performance, work," also "the performance of some science or art," from Old French operacion "operation, working, proceedings," from Latin operationem (nominative operatio) "a working, operation," from past participle stem of operari "to work, labor" (in Late Latin "to have effect, be active, cause"), from opera "work, effort," related to opus (genitive operis) "a work" (see opus). The surgical sense is first attested 1590s. Military sense of "series of movements and acts" is from 1749.

Online Etymology Dictionary, © 2010 Douglas Harper

operation in Medicine


  1. A surgical procedure, usually using instruments, for remedying an injury, ailment, defect, or dysfunction.
  2. The act, manner, or process of functioning.
The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.

operation in Science


  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.
  3. A logical operation.
  4. 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.