linguistic:paraphrasing, quality:correction
Variability

Each service is unique. It can never be exactly repeated as the time, location, circumstances, conditions, current configurations and/or assigned resources are different for the next delivery, even if the same service is requested by the consumer. Many services are regarded as heterogeneous and are typically modified for each service-consumer or for each service-context. Example: The taxi service which transports the service consumer from home to work is different from the taxi service which transports the same service consumer from work to home – another point in time, the other direction, possibly another route, probably another taxi-driver and cab. Another and more common term for this is heterogeneity.