Service (economics)
Lack of homogeneity or, Variability (Each time it is different.) - Services are typically modified for each client or each new situation. Mass production of services is very difficult. This can be seen as a problem of quality (it's not always the same). For instance, on Monday a person was driven to his work by a taxi. Next Monday, when he is driven to work by a taxi, it is not the same, even if the taxi and the driver are the same.