ICBN

The International Code of Botanical Nomenclature (ICBN) is a historic code of nomenclature that governed the naming of plants, including groups traditionally treated as algae and fungi. It established the rules for valid publication of names, the use of type specimens, the priority of names, and the formation and acceptance of new taxa, with the aim of ensuring stability and clarity in plant nomenclature.

The ICBN was developed and revised by the International Botanical Congress, with multiple editions reflecting changes in taxonomy and publication practices throughout the 20th century. It provided criteria for what constitutes a validly published name, how names are typified, and how to handle synonyms, homonyms, and new combinations. The code also addressed procedures such as the conservation or rejection of names to maintain stability in nomenclature.

In 2011, the International Botanical Congress in Melbourne adopted the International Code of Nomenclature for algae, fungi, and plants (ICN), effectively replacing the ICBN. The ICN retains many core principles of the ICBN—such as priority, typification, and the use of Latinized names—while expanding and updating rules to cover contemporary taxonomic practices and broader groups.

The ICBN is one of several nomenclatural codes used in biology and is distinct from the zoological code (ICZN) and the bacteriological code. Although the ICBN itself is no longer in force, its provisions and terminology continue to influence the ICN, which now governs the naming of all organisms covered by algae, fungi, and plants.