In zoological nomenclature, an unavailable name is a name that does not conform to the rules of the International Code of Zoological Nomenclature and that therefore is not available for use as a valid name for a taxon. 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", names without an accompanying description (nomina nuda), such as the subgeneric name Micronectomys proposed for the Nicaraguan rice rat, names proposed with a rank below that of subspecies (infrasubspecific names), such as Sorex isodon princeps montanus for a form of the taiga shrew, and various other categories.