Plants annual or perennial; monoecious, pistillate and staminate spikelets on separate rames in the same inflorescence. Culms to 3 m, erect, creeping, or floating, branched; internodes solid. Leaves not aromatic; ligules membranous. Inflorescences axillary, of 2(3) rames, 1 pistillate, the other(s) staminate, pistillate rames completely enclosed in indurate, globose to cylindric, modified leaf sheaths, termed involucres, from which the staminate rames protrude. Pistillate rames each with 3 spikelets, 1 sessile and pistillate, the other 2 pedicellate and rudimentary; sessile spikelets somewhat dorsally compressed; glumes coriaceous, beaked; stigmas protruding from the involucres. Caryopses more or less globose. Staminate rames flexible, exserted from the involucre; spikelets in pairs or triplets, 1 sessile, the other(s) pedicellate, reduced, or absent; lower glumeschartaceous, with 15 or more veins, 2-keeled, keels winged above; upper glumes similar, with 1 keel; lower florets sometimes sterile; upper florets staminate; stamens 0 or 3; lodicules 2. Pedicels not fused to the rame axes. x = 5. Name from the Greek koix, a palm.