Concept
In zoological nomenclature, the valid name of a taxon is the correct scientific name for that taxon. The valid name must be used for that taxon, regardless of any other name that may currently be used for that taxon, or may previously have been used. A name can only be valid (or invalid) when it is an available name under the International Code of Zoological Nomenclature (ICZN); if a name is unavailable, then it cannot be considered either valid or invalid. In contrast, a name which is available but not the correct name for a taxon is known as an invalid name. There are two categories of invalid names. Subjectively invalid names are names that have been rendered invalid by individual scientific judgement or opinion. Taxonomists may differ in their opinion, and names considered invalid by one researcher may be considered valid by another. They include: Junior subjective synonyms - synonyms described from different types, which were previously described as separate taxa, but are now believed to be the same taxon. The junior name is treated as invalid only so long as the two names are considered to refer to the same taxon, which is a subjective opinion. Junior secondary homonyms - In this case, the taxa are separate species, originally described in separate genera, but with the same specific name; if they are later placed in the same genus, this results in the species names being homonyms, and generally only the senior homonym can be valid. The junior name is treated as invalid only so long as the two taxa are considered to belong to the same genus, which is a subjective opinion. However, if a name became a secondary homonym prior to 1961, and was replaced by a new name, the original name may be permanently invalid. Conditionally suppressed names - these are special cases where the International Commission on Zoological Nomenclature has ruled that a name can only be valid under certain conditions (e.g., when it is not considered a synonym of a name that is junior to it), but is otherwise to be suppressed.
