Plant taxonomy or classification is the science of naming organisms and placing them in a hierarchical structure, each level being given a name (e.g., kingdom, division (phylum), class, order, family, genus, species). Taxonomic units at a given level are termed taxa (singular taxon). Names of higher order taxa (e.g., kingdom, phylum, class, order, family, genus) are uninominal (i.e., each name is a single word). Names of species are binomial (e.g., Magnolia virginiana), and names of taxa below the rank of species (e.g., subspecies, varieties) are comprised of three or more words (e.g., Panicum virgatum var. cubense). Any given organism can be classified throughout the hierarchy. For example, the species sweet bay magnolia (Magnolia virginiana) is in the genus Magnolia, the family Magnoliaceae, the order Magnoliales, the class Magnoliopsida, the division Magnoliophyta, and the kingdom Plantae. Arranging scientific plant names in a hierarchical classification allows related organisms to be classified close together (e.g., all true pines are in the genus Pinus), and this assists with information retrieval.
The PLANTS Database has several tools that permits users to search plant names throughout the classification hierarchy.