Dioscorea alata

Dioscorea alata, known as purple yam and many other names, is a species of yam, a tuberous root vegetable. The tubers are usually bright lavender in color, hence the common name, but they may sometimes be white. It is sometimes confused with taro and the Okinawa sweet potato (Ipomoea batatas cv. Ayamurasaki), although D. alata is also grown in Okinawa where it is known as beniimo(紅芋). With its origins in the Asian tropics, D. alata has been known to humans since ancient times.