Read the dictionary definition of yam. All definitions for this word.
1. edible tuberous root of various yam plants of the genus Dioscorea grown in the tropics world-wide for food
2. sweet potato with deep orange flesh that remains moist when baked
3. any of a number of tropical vines of the genus Dioscorea many having edible tuberous roots
4. edible tuber of any of several yams