The phrase nomen nudum
is a Latin term, meaning "naked name", used in taxonomy
Taxonomy is the science of identifying and naming species, and arranging them into a classification. The field of taxonomy, sometimes referred to as "biological taxonomy", revolves around the description and use of taxonomic units, known as taxa...
(especially in zoological and botanical nomenclature
Botanical nomenclature is the formal, scientific naming of plants. It is related to, but distinct from taxonomy. Plant taxonomy is concerned with grouping and classifying plants; botanical nomenclature then provides names for the results of this process. The starting point for modern botanical...
). It may or may not be written in italics, depending on style.
The term is used to indicate a designation which looks exactly like a scientific name of an organism, and may well have originally been intended to be a scientific name, but fails to be one because it has not (or has not yet) been published with an adequate description (or a reference to such a description), and thus is a "bare" or "naked" name, one which cannot be accepted as it currently stands.
Because a nomen nudum
fails to qualify as a formal scientific name, a later author can publish a real scientific name that is identical in spelling. If one and the same author puts a name in print, first as a nomen nudum
and later on publishes it for real, accompanied by a description that does meet the formal requirements, then the date of publication of the latter, formally correct publication becomes the name's date of establishment.
According to the rules of zoological nomenclature a nomen nudum
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...
; the glossary of the 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...
gives this definition:
And among the rules of that same Zoological Code:
The glossary of the International Code of Botanical Nomenclature
gives this definition: