Botanical name: Dioscorea rotundata While yams appear very similar to sweet potatoes, they're quite different. In fact, they're not even related. Yams belong to the Dioscoreae or morning glory family, while sweet potatoes are from the genus Convolvulaceae. Yams (from the African word "nyami," meaning "to eat") have only one embryonic seed leaf, while sweet potatoes have two.