A statistical classification has a structure which is composed of one or several classification levels. A classification level is often characterised by a generic name for the classification items that it regroups. For instance, the NACE uses the terms "sections", "divisions", "groups" and "classes"; the Combined Nomenclature (CN) has sections, chapters, headings, HS subheadings and CN subheadings; the NUTS includes 4 levels: Level 0 (Country), level 1 (NUTS 1), level 2 (NUTS 2) and level 3 (NUTS 3). The bottom level is always the most detailed level i.e., has the most precise information (detailed values) for the variable classifying the statistical unit. Classification levels is maintained by Eurostat and published by the Publications Office of the European Union on the EU Vocabularies website.