Binomial nomenclature: two-part scientific naming system for species

Overview of binomial nomenclature, the two-part scientific naming system that gives each species a unique genus and specific epithet, with rules for formatting, authorship, history and use across taxonomy and biological research.

In biology, the system known as binomial nomenclature gives every recognized species a two-part scientific name. Each name combines a genus name with a second term, the specific epithet; together they uniquely identify the species within the genus. The phrase literally means "two-part name."

Basic rules and formatting

Both parts are usually treated as Latin or Latinized words. In print, the full binomial is conventionally set in italics, with the genus name capitalized and the specific epithet in lower case (for example, Homo sapiens).
The same specific epithet can occur in different genera, but the full two-part combination must be unique within a kingdom or code of nomenclature.
After first use, the genus name is commonly abbreviated to its initial (e.g., H. sapiens) when context makes the meaning clear.
When a subspecies is recognized, a third name (a trinomial) is added, for example Gorilla gorilla gorilla.
Scientific names are often followed by the name of the author who published the name and the year of publication; these attributions are part of formal nomenclatural practice.

Purpose and scope

Binomial names provide a stable, internationally recognized label that avoids the ambiguity of common names. Different groups of organisms are governed by codes that set detailed rules for forming and applying names (for example, zoological and botanical codes), so a validly published name meets the criteria specified by the relevant code.

History and usage

The system was popularized in the 18th century by Carl Linnaeus and has since become the standard in scientific communication. It is used across research, conservation, environmental management, and education to ensure precise identification of organisms.

Examples and notes

Homo sapiens — the human species; here Homo is the genus and sapiens the specific epithet.
Panthera leo — the lion; the genus Panthera also includes tigers and other big cats, each with its own specific epithet.

Although binomial nomenclature is a simple idea, its practical application involves formal publication, priority, type specimens, and other rules that taxonomists follow to name and revise classifications responsibly.