Trinomen (zoological trinomial name)

Structure and formatting

Formally a trinomen consists of three words: the genus (capitalized), the species epithet (lowercase), and the subspecies epithet (lowercase). All three words are usually set in italics in print, for example Panthera tigris altaica or Canis lupus familiaris. The name of an author and year of publication may follow the trinomen but are not italicized. Abbreviations may be used after the first use, such as P. t. altaica.

Uses and importance

Trinomina are important for communicating about geographically or morphologically distinct populations that fall below the species level. They are used in taxonomy, ecological studies, conservation policy, and legal protection lists. Assigning a trinomen can affect how a population is managed or conserved, since subspecies status often highlights unique genetic or ecological traits.

Rules and distinctions

In zoology the International Code of Zoological Nomenclature provides the framework for forming and using trinomina. Botanists and other fields use different conventions: botanical infraspecific names often include a connecting term such as subsp. or var., and the codes and terminology differ from those of zoology. Thus the term trinomen is specifically common in zoological contexts.

• Examples: Ursus arctos horribilis (grizzly bear) and Gorilla gorilla gorilla (western lowland gorilla) illustrate repeated epithets when the species and subspecies names coincide.
• Formatting: genus capitalized, epithets lowercase, scientific names italicized, authorities not italicized.
• Practical note: recognition of a subspecies by trinomen can change with new research; taxonomic opinions evolve with genetic and morphological studies.

Because trinomina are tools of classification rather than fixed facts about organisms, they reflect taxonomic judgment and can be revised. For further introductory context see general resources on scientific names and zoological nomenclature.