Description from Flora of China
Herbs twining. Rootstock rhizomatous or tuberous, variable in color, shape, chemical constituents, and depth in ground. Bulblets axillary or absent. Leaves alternate or opposite, petiolate, simple or palmately compound, basal veins 3--9. Flowers unisexual (plants dioecious, rarely monoecious), arranged spirally in axillary, usually elongate spikes or racemes, or in small cymules in ± spikelike thyrses, these often several together, sometimes gathered into a terminal or axillary panicle by reduction of subtending leaves. Male flowers: stamens 6, 3 sometimes reduced to staminodes or absent. Female spikes 3.5--10 cm, few flowered. Female flowers: staminodes 3, 6, or absent. Capsule 3-winged, dehiscent apically at maturity. Seeds with a membranous wing.
Dioscorea is a genus of great economic value, including important food plants. Several species are widely cultivated in many cultivars (including Dioscorea alata D. esculenta D. japonica and D. polystachya), while other, wild species are valuable famine foods. Other species are sources of drugs both in traditional Chinese and Western medicine (notably D. nipponica and D. zingiberensis which are major sources of steroid precursors).
More than 600 species: widely distributed in tropical and temperate regions; 52 species (21 endemic, two introduced) in China.