Similarly, the International Code of Nomenclature for algae, fungi, and plants (ICN) specifies that the first published of two or more homonyms is to be used: a later homonym is "illegitimate" and is not to be used unless conserved (or sanctioned, in the case of fungi).
Under the botanical code, names that are similar enough that they are likely to be confused are also considered to be homonymous (article 53.3).
The zoological code considers even a single letter difference to be sufficient to render family-rank and genus-rank names distinct (Article 56.2), though for species names, the ICZN specifies a number of spelling variations (Article 58) that are considered to be identical.
Both codes only consider taxa that are in their respective scope (animals for the ICZN; primarily plants for the ICN).
Hemihomonyms are possible at the species level as well, with organisms in different kingdoms sharing the same binomial nomenclature.