In many American grocery stores, the vegetables labeled “yams†and “sweet potatoes†are just different varieties of sweet potatoes—when a softer, orange-fleshed variety of sweet potatoes hit the U.S. markets in the mid-20th century, they were labeled as yams to differentiate them from varieties Americans were already familiar with, and the name stuck. True yams are somewhat rare in the United States. They’re starchier than sweet potatoes, they have a slightly different shape (sweet potatoes taper toward the ends; yams stay more cylindrical and can be up to five feet long), and their skin is rough and bumpy. They’re more comparable to a white russet potato than a sweet potato, and they’re commonly used in Caribbean and West African cooking.