Any of many low, green, nonwoody plants that make up the families Poaceae (formerly Gramineae), Cyperaceae (sedges), and Juncaceae (rushes). Only the approximately 10,000 species in the family Poaceae are true grasses. They are the most economically important of all flowering plants because of their nutritious grains and soil-forming function, and they are the most widespread and most numerous of plants. The cereal grasses include wheat, corn, rice, rye, oats, barley, and millet. Grasses provide forage for grazing animals, shelter for wildlife, and construction materials, furniture, utensils, and food for humans. Some species are grown as garden ornamentals, cultivated as turf for lawns and recreational areas, or used as cover plants for erosion control. Most have hollow, segmented, round stems, bladelike leaves, and extensively branching fibrous root systems.