Basionym

Lat. basionym, from Greek βασις — "base" and ωνυμα — "name", or basionym of a biological taxon name — a name that was replaced by another using the same stem or epithet due to a change in the systematic position and (or) rank of the taxon.

In other words, a basionym is an earlier name of a biological taxon on which the current name is based.

The term "basionym" is used in botany only when there is a previous name with a useful description, and the International Code of Nomenclature for algae, fungi, and plants (ICNafp) does not require a full description of the new name. Thus, the basionym must be legitimate. Basionyms are governed by Articles 6.10, 7.3, 41, and other articles of the International Code of Nomenclature for algae, fungi, and plants.

If the current name has a basionym, then the author or authors of the basionym are indicated in parentheses at the beginning of the list of authors. If it is later found that the basionym is illegitimate, then it becomes a replaced synonym, and the list of authors of the current name must be changed so that the authors of the basionym are not mentioned.