Binomial nomenclature

Binomial nomenclature is the formal way biologists name species. Every species has a two-part scientific name. The first part is the genus, a group of closely related species, and starts with a capital letter; the second part, the specific epithet or specific name, is written in lowercase. The whole name is set in italics, or underlined when handwritten, as in Homo sapiens for humans or Escherichia coli for a common gut bacterium. After the first mention, the genus may be cut to its initial, as in E. coli.

Carl Linnaeus made the system standard in the 1750s, replacing long descriptive Latin phrases that varied from one author to the next. His Species Plantarum of 1753 is the starting point for most plant names, and the tenth edition of his Systema Naturae, published in 1758, is the starting point for animal names. Today separate international codes set the rules for naming animals, for plants, algae and fungi, and for bacteria.

Because each scientific name is unique and used worldwide, it avoids the confusion of common names, which differ between languages and regions. The epithet alone is not enough, since the same one can appear in many genera: vulgaris names both the beet, Beta vulgaris, and the common octopus, Octopus vulgaris.