Herbs, some exotic genera low shrubs, with alternate or opposite simple mostly entire thin leaves. Flowers small, green or white, perfect, monoecious, polygamous, or dioecious, bracteolate, variously clustered, usually in terminal spikes or axillary heads. Petals none. Calyx herbaceous or membranous, 2-5-parted, or 5-cleft, the segments distinct or somewhat united, equal, or the inner ones smaller. Stamens 1-5, mostly opposite the calyx-segments, hypogynous; filaments distinct, united at the base, or into a tube; anthers 1-celled or 2-celled. Ovary ovoid or subglobose, 1-celled; ovule solitary in the following genera, amphitropous (several in some tropical genera); style short, elongated or none; stigmas 1-3. Fruit a utricle, circumscissile, bursting irregularly or indehiscent, 1-seeded in our genera. Seed mostly smooth; embryo annular; endosperm mealy, usually copious.

About 40 genera and 475 species, widely distributed, most abundant in warm regions.