Priority (biology)

Priority is a principle in biological taxonomy by which a valid scientific name is established based on the oldest available name. It is a decisive rule in botanical and zoological nomenclature to recognise the first binomial name (also called binominal name in zoology) given to an organism as the correct and acceptable name. The purpose is to select one scientific name as a stable one out of two or more alternate names that often exist for a single species.

The International Code of Nomenclature for algae, fungi, and plants (ICN) defines it as: "A right to precedence established by the date of valid publication of a legitimate name or of an earlier homonym, or by the date of designation of a type." Basically, it is a scientific procedure to eliminate duplicate or multiple names for a species, for which Lucien Marcus Underwood called it "the principle of outlaw in nomenclature".