Acacia (pron.: /əˈkeɪʃə/ or /əˈkeɪsiə/), also known as a thorntree, whistling thorn or wattle, is a genus of shrubs and trees belonging to the subfamily Mimosoideae of the family Fabaceae, first described in Africa by the Swedish botanist Carl Linnaeus in 1773. Many non-Australian species tend to be thorny, whereas the majority of Australian acacias are not. They are pod-bearing, with sap and leaves typically bearing large amounts of tannins and condensed tannins that historically in many species found use as pharmaceuticals and preservatives.
The generic name derives from ἀκακία (akakia), the name given by early Greek botanist-physician Pedanius Dioscorides (ca. 40-90) to the medicinal tree A. nilotica in his book Materia Medica. This name derives from the Greek word for its characteristic thorns, ἀκίς (akis, thorn). The species name nilotica was given by Linnaeus from this tree\'s best-known range along the Nile river.
The genus Acacia previously contained roughly 1300 species, about 960 of them native to Australia, with the remainder spread around the tropical to warm-temperate regions of both hemispheres, including Europe, Africa, southern Asia, and the Americas. However, in 2005 the genus was divided into five separate genera under the tribe \"Acacieae.\" The genus Acacia was retained for the majority of the Australian species and a few in tropical Asia, Madagascar and Pacific Islands. Most of the species outside Australia, and a small number of Australian species, were reclassified into Vachellia and Senegalia. The two final genera, Acaciella and Mariosousa, each contain about a dozen species from the Americas.