Annual or perennial, erect or decumbent herbs. Stems often with hollow internodes. Leaves alternate, petiolate or subsessile, not articulate; ochreas tubular, brownish, membranous, remaining entire or shredding with age, often ciliate at apex and often with hairs on sheathing part. Flowers usually bisexual, in spikes or spike-like panicles; perianth segments 4 or 5, usually petaloid, white or pink, occasionally green, slightly enlarging in fruit; stamens 4–8, filaments filiform or subulate; stigmas 2 or 3, capitate. Nut biconvex or trigonous.
About 150 species, almost cosmopolitan; 18 species in Australia.