Annual or perennial herbs with fibrous roots, often with rhizomes. Leaves mostly tufted at the base of the culms, flat or terete or reduced to sheaths at the base of the culms. Flowers regular, bisexual, arranged in loose compound cymes or compact heads or solitary in the leaf-axils. Perianth segments 6, free, arranged in two whorls, glumaceous subherbaceous or coriaceous, green or brown to black. Stamens 3–6, free. Ovary superior, 1–3-locular; style 3-fid; ovules inserted on axile parietal or basal placentas. Fruit a capsule. 8 gen., mostly temp.