More than 100 different definitions of circular economy are used in scientific literature and professional journals. There are so many different definitions in use, because the concept is applied by a diverse group of researchers and professionals (Kirchherr, Reike & Hekkert 2017). A philosopher of science emphasizes a different aspect of the concept than a financial analyst. The diversity of definitions also makes it more difficult to make circularity measurable.
Definitions often focus on the use of raw materials or on system change. Definitions that focus on resource use often follow the 3-R approach:
Mobility can serve as a good example. Sharing cars, from companies such as MyWheels and WeGo, mean that fewer people have to buy their own cars. This reduces the use of raw materials (reduce). If the engine of a car is broken, it can be repaired or the chassis and interior of the car can be used to make or refurbish another car (reuse). When these parts can no longer be reused, the metal, textile and plastic of the parts can be melted down so that a new car can be made of them (recycling).