The plant kingdom (Kingdom Plantae) is divided into various divisions. The seed plants are in the Division Spermatophyta, the ferns and fern-allies are in Division Pteridophyta, etc. Within a division are various subdivisions. For Division Spermatophyta, the two subdivisions are Gymnospermae and Angiospermae. The latter are the angiosperms, the flowering plants. The subdivisions are further divided into classes, for Angiospermae, the classes are the Dicotylodonae and the Monocotyledonae. The classes are further subdivided into orders. Names of orders generally have the suffix -ales. For example, the Rose Order is Rosales. Within each order are one or more families. Names of families generally have the suffix -aceae, though for historical reasons, the old names of some important families are retained, for example, the Leguminosae (Bean Family) is also known as Fabaceae. A family is a group of plants which are closely related to each other. However, within some large families may be subfamilies. These are indicated by the suffix -oideae. For example, within the Leguminosae (Fabaceae) are the Mimosoideae, Caesalpinoideae, and the Papilionoideae. For very large families, the subfamilies may be further divided into tribes, which are indicated by the suffix -eae. For example, within the subfamily Mimosoideae is the tribe Adenanthereae. Every plant species is given a name, known as a binomial, because it is split into two parts: the genus (plural genera) and the specific epithet or the species name. For example, the saga tree is known as Adenanthera pavonina, with Adenanthera being the genus and pavonina being the specific epithet. Several species may fall under the same genus.
The name is in the Latin language, for various reasons. Firstly, Latin is a 'dead' language and hence does not change, unlike modern languages. Hence, the name can possibly remain in place forever without the language becoming obsolete. Secondly, the same plant can have many different names in various parts of the world, or the same name might be applied to many different plants. Hence, having a single universal name will aid communication among scientists and even the layman. Thirdly, Latin was the language of science in Europe in the past. Carl von Linne, also known as Carolus Linneaus, the famous naturalist who devised this system, first described most of the plants known then in a monumental work, the Species Plantarum. The book was written in Latin, and the standard set forth in his work is followed till today. The binomial is always italicized, the genus name is always capitalized, and the specific epithet is not capitalized. After the binomial can be found some abbreviations, e.g. Adenanthera pavonina L. These are the authors or authority, the abbreviated name of the first person who described the plant in a scientific work. For example, "L." stands for Linneaus, "Ridl." stands for H. N. Ridley, etc. Some plants may have been described by various authors as different plants, hence there may be synonyms, for example, Ficus grossularioides is also known as Ficus alba, hence it might be written Ficus grossularioides (=F. alba).