In botanical nomenclature, the ICBN prescribes a "three part name" (ternary name) for any taxon below the rank of species. The ranks below that of species explicitly allowed in the ICBN are The International Code of Botanical Nomenclature is the set of rules according to which plants are given their formal botanical names (scientific names). ... The International Code of Botanical Nomenclature is the set of rules according to which plants are given their formal botanical names (scientific names). ...

• subspecies (subspecies) - recommended abbreviation: subsp., but "ssp." is also in use
• varietas (variety) - recommended abbreviation: var.
• subvarietas (subvariety) - recommended abbreviation: subvar.
• forma (form) - recommended abbreviation: f.
• subforma (subforma) - recommended abbreviation: subf.

Such a taxon is called an infraspecific taxon. Its name consists of three parts: In zoology, as in other branches of biology, subspecies is the rank immediately subordinate to a species. ... A variety is a recognised division of a species in botany, next below the rank of subspecies; in zoology, species are only divided into subspecies and never into varieties. ... A subvariety is a recognised division of a species. ... In biology a form is a taxonomic subdivision of a species, below the level of a subspecies or variety. ...

a genus name, a specific epithet and an infraspecific epithet.

A connecting term should be placed before the infraspecific epithet to indicate the rank. It is customary to italicize all three part of a ternary name. For example:

• Acanthocalycium klimpelianum var. macranthum

• Acanthocalycium spiniflorum f. klimpelianum (Weidlich & Werderm.) Donald

The publishing author(s) of the name may (or may not) be indicated after the infraspecific epithet (except in case of an autonym). In addition publishing author(s) may be indicated after the specific epithet. A full citation would also include details of where the name was published (and possible further details).

Examples

• Adenia aculeata subsp. inermis de Wilde (identifying de Wilde as the author who published this name. Note that here it was decided not to indicate authority for the species)
• Astrophytum myriostigma subvar. glabrum Backeb.
• Pinus nigra var. pallasiana (Lambert) Asch. & Graebn. (Here, Lambert published the epithet in a name at the rank of species (Pinus pallasiana) and the taxon was subsequently reduced to a variety of Pinus nigra subsp. nigra).
• Pinus nigra J.F.Arnold subsp. salzmannii (Dunal) Franco (Here, J.F.Arnold is the author who gave the species, European black pine, its botanical name; Dunal is the author who published Pinus salzmanii being the first to use the epithet salzmannii for this taxon; Franco is the author who reduced the taxon to a subspecies in Pinus nigra)

Binomial name Pinus nigra J.F.Arnold The European Black Pine Pinus nigra (generally called Black Pine in Europe), is a variable species of pine, occurring across southern Europe from Spain to the Crimea, and also in Asia Minor, Cyprus, and locally in the Atlas Mountains of northwest Africa. ...

More than three parts

Sometimes a taxon is indicated with a listing in four or more parts e.g.

Pinus nigra J.F.Arnold subsp. salzmannii var. corsicana (Loudon) Hyl.

to indicate that the Corsican pine is a variety of the western subspecies of the European black pine. However, this is not its formal name. Its botanical name is

• Pinus nigra J.F.Arnold var. corsicana (Loudon) Hyl.

See also

• Scientific classification
• Trinomen — the term used in zoology for the trinominal name