Taxonomy is the aspect of systematics that deals with the correct application of scientific names, theories and techniques of naming, describing, and classifying organisms, and the study of the relationships of taxa, including positional changes which do not involve changes in the names of taxa. The taxonomic hierarchy is, from top to bottom: kingdom, phylum (for animals) or division (for plants and fungi), class, order, family, genus, species. In addition, taxonomy involves the study of organisms, and the similarities that varying species share, and then categorizing these organisms in relation to their ancestral lines and their common characteristics.