The definition of vegetation types at different hierarchical levels, both to study the vegetation processes and cartographics representation, is still considered a critical issue in many circles of plant ecologists. In the main part of this article, we intend to stress that concepts considered critical, such as plant associations and its ecological niche, are just operational tools that have nothing to do with the individualistic or organicismic interpretation of plant communities in vegetation sciences. We believe that plant associations as well as other higher syntaxa can be regarded as fuzzy sets in operational context to describe vegetation along environmental gradients.