Nomenclatural uniqueness is achieved through precedence, the order of preference among established names. When homonyms or synonyms exist, precedence determines the selection of accepted names. Synonyms are names that are spelled differently but refer to the same taxon. In this code, synonyms must be established clade names and may be homodefinitional or heterodefinitional. Minimum-clade, apomorphy-based, and maximum-clade definitions usually designate different clades, although they may be nested clades that differ only slightly in inclusiveness. Interpretation of the original definitional author’s clade conceptualization is based on the definition and all other information in the protologue. The protologue of an unrestricted emendation must provide evidence that the conceptualization of the clade is the same as that of the original definitional author. The protologue must also explain why the emended definition is preferable to the definition being emended.