Annual or perennial herbs or subshrubs, rarely scandent. Leaves simple, alternate or opposite, exstipulate, entire or almost so. Inflorescence a dense head, loose or spike-like thyrse, spike, raceme or panicle, basically cymose, bracteate; bracts hyaline to white or coloured, subtending one or more flowers. Flowers hermaphrodite or unisexual (plants dioecious or monoecious), actinomorphic, commonly bibracteolate, frequently in ultimate 3-flowered cymules; lateral flowers of such cymules sometimes modified into scales, spines or hooks. Perianth uniseriate, membranous to firm and finally ± indurate, usually falling with the ripe fruit included, tepals free or somewhat fused below, frequently ± pilose or lanate, green to white or variously coloured. Stamens as many as and opposite to the petals, rarely fewer; filaments free or commonly fused into a cup at the base, alternating with variously shaped pseudo-staminodes or not, sometimes almost completely fused and 5-toothed at the apex with entire or deeply lobed teeth, some occasionally anantherous. Ovary superior, unilocular; ovules 1-many, erect to pendulous, placentation basal; style very short to long and slender; stigmas capitate to long and filiform. Fruit an irregularly rupturing or circumscissile capsule (utricle) usually with thin, membranous walls, rarely crustaceous or a berry. Seeds round to lenticular or ovoid, embryo curved or circular, surrounding the ± copious endosperm.