Rice, (Oryza sativa), edible starchy cereal grain and the grass plant (family Poaceae). Rice is normally grown as an annual plant, and irrigated by flooding the fields while, or after, setting the seedlings. Rice is a good source of protein and a staple food in many parts of the world, cooked white rice is 69% water, 29% carbohydrates, 2% protein, and contains negligible fat. In a reference serving of 100 grams (3.5 oz), cooked white rice provides 130 calories of food energy, and contains moderate levels of manganese (18%), with no other micronutrients in significant content.