Perennial, rarely annual plants; caespitose or rhizome creeping, often stoloniferous, sometimes tuberiferous or with bulbils. Stem mostly scapose, solid, trigonous, without hairs, but scabrous along edges, often cylindrical, smooth. Leaves in three ranks, mostly basal or subbasal, with sheaths, with or without ligules, blades usually glabrous, but apex and margins barbed; blades reduced in several groups. Inflorescence a spike, multiple spike or large compound, crateriform anthelodium; glumes spirally or distichously arranged. Flowers bisexual or unisexual, seldom dioecious; perfect flowers with or without bristle-like perianth, with 1-3 stamens, rarely more, and 2-3 stigmas; unisexual flowers composed of stamens in axil of glume, or gynoecium in axil of prophyll (utricle). Nut trigonous or bi-convex, sometimes winged.