Yams are tropical by nature and should not be confused horticulturally with the sweet potato. Yams are sometimes called "true yams", "greater yam", "tropical yam" and "name" (that last one is a two syllable word pronounce naw- may). Most true yams are vining crops that grow in the tropics (Puerto Rico, Costa Rica, Jamaica, Virgin Islands) with a white flesh and texture similar to a turnip. Yams belong to several genera including Dioscorea.

Fleshy, moist sweet potatoes, mainly from Louisiana, have been misnamed as yam. Candied yams commonly purchased in cans for the holidays are in reality a sweet potato with the genus "Ipomea".

Boniatos are a type of sweet potato, commonly referred to as Cuban Sweet Potato, though they are tropic in origin and look more like a yam.