Taxonomy is a practice and science focused on classification and categorization. It involves developing a scheme of classes and allocating things to these classes.
While originally used for classifying organisms, taxonomy now has broader applications, including organizing documents, videos, or any other items. Taxonomies arrange units called "taxa" and often form hierarchies, though they can also include network structures with multi-parent relationships.
In a mathematical sense, a hierarchical taxonomy is a tree structure of classifications for a set of objects. It starts with a root node that applies to all objects and branches into more specific classifications.
Taxonomies frequently use "is-a" relationships, where each level is a subset of the one above it. In linguistics, these relationships are known as hyponymy, with broader terms called hypernyms and narrower terms called hyponyms. This structure allows for the organization of concepts from general to specific.