Annuals or perennials, herbaceous, often aquatic; of variable habit. Inflorescence a contracted spike-like or rarely open panicle with rather small, often densely clustered spikelets. Spikelets solitary, pedicelled, falling entire at maturity, 2-flowered; lower floret ♂ or Ø, upper floret ☿. Glumes very unequal in length, of similar texture, softly to rigidly membranous, or the lower reduced to a scale and the upper = spikelet, often basally gibbous, (5)-7-9-(13)-nerved. Lower floret: lemma ≈ upper glume but straighter; palea ≈ lemma, finely 2-keeled, or palea almost 0. Upper floret: lemma very convex, chartaceous to subcrustaceous, obscurely 5-nerved; palea = lemma, of similar texture, 2-nerved, scarcely keeled; lodicules 2, small, broadly cuneate, fleshy, glabrous; stamens 3; ovary apex glabrous, stigmas free, terminal or subterminal; caryopsis compressed, embryo c. half length of caryopsis, hilum punctiform.