Open nomenclature is a vocabulary of partly informal terms and signs in which a taxonomist may express remarks about their own material.
This is in contrast to synonymy lists, in which a taxonomist may express remarks on the work of others.
[1] Commonly such remarks take the form of abbreviated taxonomic expressions in biological classification.
[2]: 223 There are no strict conventions in open nomenclature concerning which expressions to use or where to place them in the Latin name of a species or other taxon, and this may lead to difficulties of interpretation.
However, the most significant unsettled issues concern the way that their meanings are to be interpreted.