Herbs or small shrubs with glabrous to densely hairy stems. Leaves opposite or verticillate, in whorls of 3(–6), the blades mostly narrow, more rarely ovate or oblong; stipule-sheath adnate to the petioles at base with mostly 1 or less often 2–3 narrow lobes. Flowers mostly small or very small, dioecious, polygamous or hermaphrodite, axillary, sessile or rarely in panicles; bracts minute, 2–3 at base of the ovary. Calyx-tube ovoid, ellipsoid or obovoid, the limb mostly minute, 4–5-toothed or 2–4-lobed, the lobes sometimes ovate. Corolla in ♂ flowers with tube campanulate, funnel-shaped or cylindrical, lobes 4(–5), linear to elliptic-lanceolate, longer or shorter than the tube, often revolute; stamens exserted, the filaments variously inserted at base or the throat of tube; styles 2, or joined at base, often short in ♂ flowers but exserted in hermaphrodite ones; in ♀ flowers the corolla-tube is often very minute with 2–4 reduced erect lobes; styles 2, or joined at the base, the stigmas long and feathery hairy; in certain species they are sometimes very long in certain specimens and form a tangled skein falling over the foliage. Ovary 2-locular, each locule containing a single erect ovule. Fruit separating septicidally into 2 cocci, each compressed ellipsoid, ventrally plane or grooved, dorsally convex, indehiscent or sometimes dehiscing ventrally. Seeds conforming in shape to the cocci.