Basionym

In the scientific name of organisms, basionym or basyonym^[1][2] means the original name on which a new name is based; the author citation of the new name should include the authors of the basionym in parentheses. The term "basionym" is used in both botany and zoology.^[3] In zoology, alternate terms such as original combination^[4] or protonym^[3][5] are sometimes used instead. Bacteriology uses a similar term, basonym, spelled without an i.^[6]

Although "basionym" and "protonym" are often used interchangeably, they have slightly different technical definitions. A basionym is the correct spelling of the original name (according to the applicable nomenclature rules), while a protonym is the original spelling of the original name.^[5] These are typically the same, but in rare cases may differ.

When creating new taxonomic names, there are specific rules about how basionyms can be used. A new combination or name at new rank must be based directly on the original basionym rather than on any intermediate combinations. This means that if a species is transferred between multiple genera over time, each new combination must refer back to the original name rather than to more recent combinations. This helps maintain a clear chain of nomenclature and prevents confusion about the ultimate source of the name. For example, when transferring a species that has already been moved to a different genus, taxonomists must cite the original species name as the basionym, not the intermediate combination.^[7]