Fraxinus (Ash) is a genus flowering plant in the olive and lilac family, Oleaceae. It contains 45-65 species of usually medium to large trees, mostly deciduous though a few subtropical species are evergreen. The tree's common English name, Ash, goes back to the Old English ęsc, while the generic name originated in Latin. Both words also meant "spear" in their respective languages. The seeds, popularly known as keys or helicopter seeds, are a type of fruit known as a samara.