  Several different versions of the theory of numerosities have been introduced
in the literature. Here, we unify these approaches in a consistent frame
through the notion of set of labels, relating numerosities with the Kiesler
field of Euclidean numbers. This approach allows to easily introduce, by means
of numerosities, ordinals and their natural operations, as well as the Lebesgue
measure as a counting measure on the reals.
