Herbs erect or climbing subshrubs. Leaves opposite, margin entire or serrate. Flowers perfect or unisexual on different plants, very small, solitary or clustered in spikes and again arranged into complex thyrsoid structures. Bracts and bracteoles often shiny, membranous. Tepals 5, membranous, long hairy or nearly glabrous, base not rigid. Stamens 5; pseudostaminodes very small or absent in female flowers. Ovary compressed; style very short or absent; stigmas 2, rarely 3, subulate; ovule 1, pendulous. Utricles globose, compressed, indehiscent. Seeds shiny, lenticular or reniform.

About 70 species: tropical Asia, North and South America, Pacific Islands; one species (introduced) in China.