In botanical nomenclature, a type (typus, nomenclatural type)
- "is that element to which the name of a taxon is permanently attached ..." (Art 7.1 ICBN).
A botanical name, by itself, is only a phrase (of one to three words). For a name to be meaningful it is necessary to be sure what it applies to. A type fixes a botanical name to a taxon. In botany a type is either a specimen or an illustration. A specimen is a real plant (or one or more parts of a plant or a lot of small plants), dead and kept safe, "curated", in a herbarium (or the equivalent for fungi). Notable cases of where an illustration may serve as a type are (this is not an exclusive listing):
- A detailed drawing, painting, etc, depicting the plant, from the early days of plant taxonomy (as we now know it). In those days a dried plant was difficult to transport and hard to keep safe for the future: many specimens that famous botanists looked at have since been lost or damaged. However, there were devoted botanical artists who upon assignment by a botanist (or naturalist) could make a faithful and detailed work of botanical art, for inclusion in a costly book.
- A detailed picture of something that can be seen only through a microscope. A tiny 'plant' on a microscope slide makes for a poor type: the microscope slide may be lost or damaged, or it may be very difficult to find the 'plant' in question among whatever else is on the microscope slide. An illustration makes for a much more reliable type (Art 37.5 of the Vienna Code, 2006).
Note that a type only fixes a name to a single representative of the taxon. A type does not determine the circumscription of the taxon. For example, the common dandelion is a controversial taxon: some botanists consider it to consist of over a hundred species, although most botanists regard it to be a single species. The type of the name Taraxacum officinale is the same whether the circumscription of the species includes all those small species (Taraxacum officinale is a 'big' species) or whether the circumscription is limited to only one small species among the other hundred (Taraxacum officinale is a 'small' species). In this case the name Taraxacum officinale is the same and the type of the name is the same, but the extent of what the name actually applies to varies strongly. Setting the circumscription of a taxon is done by a taxonomist in a publication.
- Usually, only a species or an infraspecific taxon can have a type of its own. For a new taxon (published on or after 1 January 1958) at these ranks a type should not be an illustration.
- A genus (almost always) has the same type as that of one of its species. For convenience this species may, unofficially, be called its type species, a phrase that has no standing under the ICBN. Only by conservation may a genus have its own type.
- A family has the same type as that of one of its genera (that is, almost always the type of a species). For convenience this genus may, unofficially, be called its type genus, a phrase that has no standing under the ICBN.
- The ICBN provides a listing of the various kinds of type in Art 9, the most important of which is the holotype. Note that the word "type" appears in botanical literature as a part of several terms that have no status under the ICBN: for example a clonotype.
- Type (zoology)