Annual or perennial grass-like herbs with short or long rhizomes. Culms trigonous to triquetrous or rarely cylindric and septate (Cyperus articulatus). Leaves narrow, with closed sheaths, sometimes with a ligule opposite to the blade. Inflorescence consisting of a solitary spikelet or capitulum, or many spikelets in heads or spikes or simple to compound umbels. The branches often subtended by conspicuous bracts. Flowers in the axil of a glume, bisexual or unisexual, usually consisting of 1—3 stamens and/or one pistil, sometimes provided with a perigon of bristles. Glumes distichous or spirally arranged. Stamens with slender or filiform filaments. Ovary 1-celled; style 2—3-branched. Fruit a nut. Endosperm mealy. About 3200 species in nearly 80 genera, all over the world.