The second line isn't a part of the song, "Let's Call The Whole Thing Off." It's just me making a point.
I have heard sweet potatoes called yams, and vice versa. But the two have differences, which go beyond pronunciation. As the season begins in the States for sweet potato pies and candied yams, let's take an overview of the veggies.
Yams are the tubers of a tropical vine native to Africa and Asia. They are also popular in Latin American and Caribbean markets. There are hundreds of different varieties. Yams are high in vitamins C and B6, fiber, manganese and potassium. They have more natural sugar than sweet potatoes.
Sweet potatoes are the tubers of a plant native to the tropical parts of South America, and eventually became cultivated in the Southern U.S. They are high in beta carotene, fiber and vitamins C and B6. A variety known as white sweet potatoes have pale yellow flesh and pale skin. Its taste is not sweet, and its texture is hard like white potatoes. The variety of sweet potato in which the skin is more orange in color and has a softer, dark orange flesh is what is often mistaken for a yam.
According the website, Everyday Mysteries: Fun Science Facts from the Library of Congress, The U.S. Department of Agriculture requires labels with the term "yam" to be accompanied by the term "sweet potato." It states, "Unless you specifically search for yams, which are usually found in an international market, you are probably eating sweet potatoes!"
So, you need to make sure your yam is indeed a yam. Otherwise, you might be sweet potato duped. Though, I don't think you can go wrong with either vegetable. They are both tasty tubers.