CHAPTER I. TAXA AND THEIR RANKS

Article 5

5.1. The relative order of the ranks specified in Art. 3 and 4 must not be altered (see Art. 33.9 and 33.12).

Recommendation 5A

5A.1. For purposes of standardization, the following abbreviations are recommended: cl. (class), ord. (order), fam. (family), tr. (tribe), gen. (genus), sect. (section), ser. (series), sp. (species), var. (variety), f. (forma). The abbreviations for additional ranks created by the addition of the prefix sub-, or for nothotaxa with the prefix notho-, should be formed by adding the prefixes, e.g., subsp. (subspecies), nothosp. (nothospecies), but subg. (subgenus).