Domesticated Rice comprises two species in the Poaceae ("true grass") family, Oryza sativa and Oryza glaberrima. These plants are native to tropical and subtropical southern Asia and southeastern Africa. Rice provides more than one fifth of the calories consumed by humans in their global diets. (The term "wild rice" can refer to the wild species of Oryza, but conventionally refers to species of the related genus Zizania, both wild and domesticated.) Rice is a monocarpic annual plant, growing to 1–1.8 m tall, occasionally more depending on the variety and soil fertility. The grass has long, slender leaves 50–100 cm long and 2–2.5 cm broad. The small wind-pollinated flowers are produced in a branched arching to pendulous inflorescence 30–50 cm long. The seed is a grain (caryopsis) 5–12 mm long and 2–3 mm thick.
Rice is a staple for a large part of the world's human population, especially in East, South and Southeast Asia, making it the most consumed cereal grain. It is estimated that more than 2 billion people rely on rice as their primary source of nutrition everydaycitation needed]. Rice is the world's largest crop (700 million metric tons in 2005), with maize ("corn") (694 million metric tons in 2005) and wheat (626 million metric tons in 2005) behind it.citation needed] Rice cultivation is well-suited to countries and regions with low labour costs and high rainfall, as it is very labour-intensive to cultivate and requires plenty of water for irrigation, much like the licorice crops found in Eastern Europe. Rice can be grown practically anywhere, even on steep hillsides. Although its species are native to South Asia and certain parts of Africa, centuries of trade and exportation have made it commonplace in many cultures.