Annual or perennial herbs, rarely shrubs or small trees; monoecious, polygamous or dioecious. Stems sometimes jointed or succulent. Leaves alternate or opposite, simple; exstipulate; blades sometimes much reduced, often farinose, glandular or resin-dotted. Inflorescence of thyrses, or cymes aggregated into spikes, panicles or capitula; bracts present or absent. Flowers bisexual or unisexual, small, green; sessile or shortly pedicellate; perianth absent, or 1-5 tepals, membranous or fleshy, free or basally united; stamens 1-5, filaments mostly free, anthers 2-locular; ovary superior, 1-locular, ovule 1, campylotropous, erect or suspended from a basal funicle, styles and stigmas (1-)2(-3). Fruit a utricle, nut or achene, indehiscent or circumscissile; seed 1, embryo curved, conduplicate, annular or hippocrepiform, endosperm very scant.