In zoological nomenclature, an unavailable name is a name that does not conform to the rules of the International Code of Zoological Nomenclature

International Code of Zoological Nomenclature

The International Code of Zoological Nomenclature is a widely accepted convention in zoology that rules the formal scientific naming of organisms treated as animals...

 and that therefore is not available for use as a valid name for a taxon

Taxon

|thumb|270px|[[African elephants]] form a widely-accepted taxon, the [[genus]] LoxodontaA taxon is a group of organisms, which a taxonomist adjudges to be a unit. Usually a taxon is given a name and a rank, although neither is a requirement...

. Such a name does not fulfil the requirements in Articles 10 through 20 of the Code, or is excluded under Article 1.3.

Unavailable names include names that have not been validly published, such as "Oryzomys hypenemus

Oryzomys hypenemus

"Ekbletomys hypenemus" is an extinct oryzomyine rodent from the islands of Antigua and Barbuda, Lesser Antilles. It was described as the only species of the subgenus "Ekbletomys" of genus Oryzomys in a 1962 Ph.D. thesis, but that name is not available under the International Code of Zoological...

", names without an accompanying description (nomina nuda

Nomen nudum

The phrase nomen nudum is a Latin term, meaning "naked name", used in taxonomy...

), such as the subgeneric name Micronectomys proposed for the Nicaraguan Rice Rat

Nicaraguan Rice Rat

Oryzomys dimidiatus, also known as the Nicaraguan Oryzomys, Thomas's Rice Rat, or Nicaraguan Rice Rat, is a rodent in the genus Oryzomys of the family Cricetidae. It is known from only three specimens, all collected in southeastern Nicaragua since 1904...

, names proposed with a rank below that of subspecies

Subspecies

Subspecies in biological classification, is either a taxonomic rank subordinate to species, ora taxonomic unit in that rank . A subspecies cannot be recognized in isolation: a species will either be recognized as having no subspecies at all or two or more, never just one...

 (infrasubspecific names), such as Sorex isodon princeps montanus for a form of the Taiga Shrew

Taiga Shrew

The Taiga Shrew , also known as the Even-toothed Shrew can achieve a body length of about 67 millimeters, with a tail of about 43 millimeters. This shrew is very similar to the Long-Clawed Shrew. This species inhabits forested mountain valleys, and is found across northern Eurasia...

, and various other categories.