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 scheme for assessing claims to come into operation (= start working) early next year.FunctioningPerforming a function›[U]the way that parts of a machine or system work together, or the process of making parts of a machine or system work togetherPerforming a functionFunctioningC1[C]a business organization: Less profitable business operations will have difficulty in finding financial support.Businesses and enterprisesC1[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.Acting and actsDealing with things or people