The word "cereal" comes from Ceres, a pre-Roman goddess of agriculture. Cereal includes any plant from the grass family that yields an edible grain (seed). The most popular grains are barley, corn, millet, oats, quinoa, rice, rye, sorghum, triticale, wheat and wild rice. Because cereals are inexpensive, are a readily available source of protein and have more carbohydrates than any other food, they're a staple throughout the world. See also spelt; teff.