A yam is a root vegetable which is like a potato, and grows in tropical regions.
2. variable noun
Yams are the same as sweet potatoes.
[US]
yam in British English
(jæm)
noun
1.
any of various twining plants of the genus Dioscorea, of tropical and subtropical regions, cultivated for their edible tubers: family Dioscoreaceae
2.
the starchy tuber of any of these plants, which is eaten as a vegetable
3. Southern US
any of certain large varieties of sweet potato
4. a former Scot name for the (common) potato
Word origin
C17: from Portuguese inhame, ultimately of West African origin; compare Senegal nyami to eat
yam in American English
(jæm)
noun
1.
a.
the edible, starchy, tuberous root of any of several tropical climbing plants (genus Dioscorea) of the yam family, widely grown in the tropics for food
b.
any of these plants
2.
any of various other similar plants, as the barbasco
3. US
a moist, orange-colored variety of sweet potato
4. Scottish, Obsolete
potato (sense 2)
adjective
5.
designating a family (Dioscoreaceae, order Liliales), of climbing, chiefly tropical monocotyledonous plants, including the barbasco