Yam n. : A large, esculent, farinaceous tuber of various climbing plants of the genus Dioscorea; also, the plants themselves. Mostly natives of warm climates. The plants have netted-veined, petioled leaves, and pods with three broad wings. The commonest species is D. sativa, but several others are cultivated.

Example:
I want to plant wild Yam at my backyard, Where can I find the plants?

Taxonomy
yam, tubers, vegetable, species, Africa, Yam Festival, varieties, vines, Kay, sweet potatoes, food, yams and sweet potatoes, air potato, raw yams, pounded yam, ingredient, purple yam, Walsh.

Defination from the web:
... Yam is the common name for some species in the genus Dioscorea (family Dioscoreaceae) ... There are many cultivars of yam. ...