ABSTRACT
Some objects do not extend in space, like the geometrical or mechanical point that has no volume, no surface, and no length. Some others do occupy a piece of the universe but in such a way that there is no distinction between the various elements that comprise them. They are homogeneous in the sense that each geometrical element of the object has the same properties whatever the localization or the shape of the element. Some others extend in space too, but with a dependence of their element properties on their geometrical shape or on their location in space. They are spatially heterogeneous objects.
