1.  yam(n = noun.plant) - edible tuber of any of several yams;
is a kind of tuber
is a part of yam, yam plant

2.  yam(n = noun.plant) yam plant - any of a number of tropical vines of the genus Dioscorea many having edible tuberous roots;
is a kind of vine
has parts: yam
is a member of dioscorea, genus dioscorea
has particulars: dioscorea alata, water yam, white yam, chinese yam, cinnamon vine, dioscorea batata, air potato, dioscorea bulbifera, cush-cush, dioscorea trifida

3.  yam(n = noun.food) - sweet potato with deep orange flesh that remains moist when baked;
is a kind of sweet potato

4.  yam(n = noun.food) - edible tuberous root of various yam plants of the genus Dioscorea grown in the tropics world-wide for food;
is a kind of root vegetable

1.  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 Dioscorea sativa, but several others are cultivated. [1913 Webster]

2.  Any one of several cultural varieties of the sweet potato. [Webster 1913 Suppl.]

yam, n.
1 a any tropical or subtropical climbing plant of the genus Dioscorea. b the edible starchy tuber of this.
2 US a sweet potato.

Etymology:
Port. inhame or Sp. i{ntilde}ame, of unkn. orig.

N  vegetable, vegetable kingdom, flora, verdure, plant, tree, shrub, bush, creeper, herb, herbage, grass, annual, perennial, biennial, triennial, exotic, timber, forest, wood, woodlands, timberland, hurst, frith, holt, weald, park, chase, greenwood, brake, grove, copse, coppice, bocage, tope, clump of trees, thicket, spinet, spinney, underwood, brushwood, scrub, boscage, bosk, ceja, chaparal, motte, arboretum, bush, jungle, prairie, heath, heather, fern, bracken, furze, gorse, whin, grass, turf, pasture, pasturage, turbary, sedge, rush, weed, fungus, mushroom, toadstool, lichen, moss, conferva, mold, growth, alfalfa, alfilaria, banyan, blow, blowth, floret, petiole, pin grass, timothy, yam, yew, zinnia, foliage, branch, bough, ramage, stem, tigella, spray, leaf, flower, blossom, bine, flowering plant, timber tree, fruit tree, pulse, legume, vegetable, vegetal, vegetive, vegitous, herbaceous, herbal, botanic, sylvan, silvan, arborary, arboreous, arborescent, arborical, woody, grassy, verdant, verdurous, floral, mossy, lignous, ligneous, wooden, leguminous, vosky, cespitose, turf-like, turfy, endogenous, exogenous, green-robed senators of mighty woods, this is the forest primeval.

chinese yam, elephant yam, water yam, white yam, wild yam, yam bean, yam family, yam plant