A nomenclatural type is a specimen selected to serve as a permanent reference for the name of a plant. As a result, these specimens are extremely important for the correct application of plant names. (For full information)
There are several different categories of types; the most common are:
Holotype: The single specimen designated as the type of a name by the original author.
Isotype: Any duplicate specimen of the holotype.
Syntype: Any of two or more specimens listed in an original description published before 1958, when the International Code of Nomenclature did not yet prescribe the designation of nomenclatural types.
Paratype: A specimen not formally designated as a type but cited along with the type collection in the original description of a taxon.
Lectotype: A specimen chosen by a later researcher to serve as if it was the holotype. It is chosen among the syntypes.
Neotype: A specimen chosen by a later researcher to serve in place of a holotype when all specimens available to the original publishing author of a scientific name have been lost or destroyed.