The systematic botany that deals with the giving of names to plants is known as nomenclature.
The purpose of names is to act as easy means of reference. It is important to understand that it is further to identification and classification.
The common or vernacular names of the plants are many and are restricted to the people of one language or even to one region of a country.
Common names cannot be universal as it varies from region to region, place to place and country to country. This made necessary the need for assigning scientific names to the plants to facilitate communicating, writing and exchanging information about a particular plant.
For scientific plant nomenclature, a set of rules has been drawn up. It is known as International Code of Botanical Nomenclature (ICBN) and it governs the formation and usage of all scientific names except those of cultivars. These are governed by a separate code, the International Code of Nomenclature for Cultivated Plants (ICNCP).
A fundamental provision of the International Code of Botanical Nomenclature is that specific plant names must be Latin ones or at least treated as such even if derived from other languages.
The scientific name of a plant consists of two parts- first part refers to the generic name or genus and the second part refers to the specific name or species.
This is known as binomial nomenclature. Botanical names are often followed by the name of a person, this is the authority citation and the person is said to be author of the name. Author of a name is the person who first published that name. His name is not a part of botanical name but is added for purpose of precision.
The great strength of binomial system of nomenclature is that it provides a summary of affinities which enables us to make inferences about plants unknown to us. For example: the groundsel is Senecio vulgaris and the oxford ragwort is Senecio squalidus. If we are familiar with the groundsel but not with the oxford ragwort we can infer, since they are both species of Senecio, that oxford ragwort will resemble groundsel in some respects. If we have to cultivate oxford ragwort, then we can predict the cultivation requirements with some degree of certainty.
Sometimes new information coming to light pose special problems in deciding the nomenclature and calls for a change. If it is found that any species has been placed in wrong genus, and has to be transferred to another, its name will inevitably be changed.