In scientific nomenclature, a synonym is a scientific name that applies to a taxon that (now) goes by a different scientific name,[1] although zoologists use the term somewhat differently.[2] For example, Linnaeus was the first to give a scientific name (under the currently used system of scientific nomenclature) to the Norway spruce, which he called Pinus abies. This name is no longer in use: it is now a synonym of the current scientific name which is Picea abies.

Unlike synonyms in other contexts, in taxonomy a synonym is not interchangeable with the name of which it is a synonym. In taxonomy, synonyms are not equals, but have a different status. In general, for any taxon with a particular circumscription, position and rank only one scientific name is considered to be the correct one at any given time (this correct name is to be determined by applying the relevant code of nomenclature). A synonym is always the synonym of a different scientific name and cannot exist in isolation. Given that the correct name of a taxon depends on the taxonomic viewpoint used (resulting in a particular circumscription, position and rank) a name that is one taxonomist's synonym may be another taxonomist's correct name (and vice versa).