Nomina dubia

In zoological nomenclature, a nomen dubium (Latin for "doubtful name", plural nomina dubia) is a scientific name that is of unknown or doubtful application.

In bacteriological nomenclature, nomina dubia may be placed on the list of rejected names by the Judicial Commission. The meaning of these names is uncertain. Other categories of names that may be treated in this way (rule 56a) are:

• ambiguous names, nomina ambigua, have been used with more than one meaning
• names causing confusion, nomina confusa, are based on a mixed culture
• perplexing names, nomina perplexa, confusingly similar names
• perilous names, nomina periculosa, names that may lead to accidents endangering life or health or with potential serious economic consequences

In botanical nomenclature the phrase nomen dubium has no status, although it is informally used for names whose application has become confusing. In this regard however, its synonym nomen ambiguum is of more frequent use. In botany, such names may be proposed for rejection.