noun
(uncountable) The method by which a device performs its function.
(uncountable) The method or practice by which actions are done.
(uncountable) The act or process of operating (verb): agency; the exertion of power, physical, mechanical, or moral.
(countable) A planned undertaking.
(countable) A business or organization.
(countable, medicine) A surgical procedure.
(computing, logic, mathematics, countable) A procedure for generating a value from one or more other values (the operands).
(military, countable) A military campaign (e.g. Operation Desert Storm).
(obsolete, countable) Effect produced; influence.