1. The act or process of operating or functioning.
2. The state of being operative or functional: a factory in operation.
3. A process or series of acts involved in a particular form of work: the operation of building a house.
4. An instance or method of efficient, productive activity: That restaurant is quite an operation.
5. An unethical or illegal business: a fencing operation for stolen goods.
6. Medicine A surgical procedure for remedying an injury, ailment, defect, or dysfunction.
7. Mathematics A process or action, such as addition, substitution, transposition, or differentiation, performed in a specified sequence and in accordance with specific rules.
8. A logical operation.
9. Computers An action resulting from a single instruction.
a. A military or naval action, campaign, or mission.
b. operations The headquarters or center from which a military action, flights into and out of an airfield, or other activities are controlled.
11. operations The division of an organization that carries out the major planning and operating functions.
The American Heritage® Dictionary of the English Language, Fifth Edition copyright ©2020 by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
Indo-European & Semitic Roots Appendices
Thousands of entries in the dictionary include etymologies that trace their origins back to reconstructed proto-languages. You can obtain more information about these forms in our online appendices:
The Indo-European appendix covers nearly half of the Indo-European roots that have left their mark on English words. A more complete treatment of Indo-European roots and the English words derived from them is available in our Dictionary of Indo-European Roots.