Is there a crystal clear definition of a crystal?

Abstract

To clearly define the objects one is working with is a prerequisite for sound scientific work. In particular, a comparison of results is impossible without. In this view, one needs a clear-cut definition of what a crystal is supposed to be. Moreover, in view of the large community of people working with them, it is desirable to even have a well accepted definition. Neither property seems to be satisfied with the present fuzzy definition of a crystal, and the reasons are manifold. …