Why Do Scientific Names Have Two Parts?

Biologists have identified and described millions of species on Earth, from towering redwoods to microscopic bacteria, and each one has a name that is clear, consistent, and recognized worldwide. To accomplish this, biology uses a standardized system known as binomial nomenclature to uniquely name the diverse organisms of our planet. Developed in the 18th century by the Swedish naturalist Carolus Linnaeus, this system provides every described species with a two-part scientific name. These two fundamental parts are the genus, which groups closely related organisms, and the species, which distinguishes one related organism from another within the group. Unlike common names—which can vary across languages and regions, or even refer to multiple different organisms—a scientific name is precise and universal, allowing people everywhere to communicate clearly about the same species. In addition, because species that share a genus are closely related, a binomial name also conveys important information about an organism’s evolutionary relationships.

Examples

Let’s look at the scientific name for the common peach, Prunus persica. Prunus indicates the genus, which, in this case, includes other familiar fruit trees, such as the cherry, plum, almond, and apricot. All these trees are very closely related, so all have Prunus in their binomial names. The species name persica distinguishes the peach from other members of the genus, such as the apricot, which is Prunus armeniaca, and the almond, which is Prunus dulcis; persica refers to Persia (modern-day Iran), where peaches were once thought to have originated.

Some scientific names have three parts: the genus, the species, and a subspecies. For example, the domestic dog is called Canis lupus familiaris. Here the subspecies, familiaris, indicates that the dog is directly descended (through domestication) from the gray wolf, Canis lupus.

Rules and meanings

Scientific names are usually derived from Latin or Latinized Greek. Latin was chosen because it was the language of Western scholarship in Linnaeus’s time and is considered a “dead” language—it is no longer used in ordinary conversation and thus its meanings do not change over time. Many scientific names describe an organism’s appearance, behavior, habitat, or geographic origin. For example, aquaticus is a common species epithet that indicates an aquatic plant or animal, such as the water tupelo (Nyssa aquatica). Similarly, the species epithet borealis (“northern”) is used for a number of plants and animals found in the far north, such as twinflower (Linnaea borealis), while australis (“southern”) indicates organisms with a distribution in the far south, such as the Australian anchovy (Engraulis australis).

Some organisms are named in honor of people, though modern scientists are generally discouraged from naming a species after themselves. Many bear the names of famous scientists or explorers, such as Magnolia, after the French botanist Pierre Magnol, and the bacterium Escherichia coli, which honors the German-Austrian bacteriologist and pediatrician Theodor Escherich. Beloved English broadcaster and naturalist David Attenborough has more than 50 organisms named in his honor. Some scientific names are in tribute to things or fictional characters, such as the fungus Spongiforma squarepantsii, discovered in 2010 and named for its resemblance to the cartoon character SpongeBob SquarePants. In 2024 a genus of Chinese ground spiders was named Hotwheels after the toy model cars.

Because scientific names follow Latin grammar, the words must follow certain rules of agreement. The species name often functions like an adjective and must agree with the genus in grammatical gender and number. For example, the red maple is Acer rubrum—rubrum is a neuter form of “red” that matches the neuter gender of Acer. If the same descriptive word were paired with a feminine genus, its ending would change. These grammatical adjustments help maintain consistency within the naming system. There are separate international codes of nomenclature in botany (first published in 1901), in zoology (1906), and in microbiology (bacteria, 1948).