Annual or perennial herbs, usually ± succulent, glabrous, rarely hairy. Stems erect or prostrate, long and many-noded or almost 0. Leaves alternate, entire, with basal, membranous, closed sheath. Flowers bisexual, usually actinomorphic, usually in terminal simple or compound cymes or panicles, sometimes in axillary clusters, rarely solitary; sepals 3, green, herbaceous, usually free; petals 3, coloured or white, equal or unequal, free or rarely united in a tube, ± ephemeral or deciduous. Stamens usually 6, occasionally 3, rarely 1, fertile and remainder reduced to staminodia. Ovary superior, 3-(2)-locular; ovules few to solitary in each locule; style simple; stigma capitate or rarely 3-fid. Fruit a loculicidal 2-3-celled capsule occasionally enclosed by fleshy sepals, rarely fruit fleshy and indehiscent. Seeds few to many. About 40 genera, mainly of tropical and subtropical regions.