A generic name may be abbreviated to the initial letter followed by a period, for the second and subsequent citations in a single context, but only under conditions that leave no ambiguity. However, at the beginning of a sentence, which should never begin with an abbreviation, the genus name should be written in full (e.g. 'Baculites compressus is elongate').

The name of a subdivision of a genus is placed in parentheses following the generic name, e.g. Scaphites (Hoploscaphites) constrictus. Subsequent citations may be written as S. (H.) constrictus. This form may be used in both zoological and botanical citations. However, according to the ICBN, in normal citation the subdivisional name consists of the generic name and a subdivisional epithet connected by a term, as for example Costus subg. Metacostus.

A trivial name follows the generic name and begins with a lower case letter. It may be abbreviated only when followed by a subtrivial name (see below). It is not recommended that the trivial name alone be used in citations of biostratigraphic units (e.g. compressus Zone). Instead, Baculites compressus Zone, or B. compressus Zone should be used.

A subtrivial name always follows the species name, and its first letter, like that of the trivial name, is always lower case. In zoological citations it may be written as Coelospira exilicosta orbita or as C. e. orbita for subsequent citations. In botanical citations, the subspecies (or other infraspecific) name is connected to the species name by a term denoting its rank. For example: Stachys palustris subsp. pilosa.