Plants monoecious or dioecious, with stinging hairs. Leaves opposite, decussate, petiolate, simple, toothed to incised, very rarely almost entire; mostly 3- or 5-veined at base; petiolate, stipulate. Inflorescence axillary, paired compact or elongate, interrupted spikes or panicles, unisexual or bisexual. Flowers deeply 4-lobed. Male flowers with perianth lobes equal; stamens 4; pistillode present. Female flowers with the 2 inner perianth lobes enlarged; pistil straight; style short or absent; stigma tufted, many-armed. Achene laterally compressed, ovoid, enclosed within persistent perianth.
About 100 species, mostly in temperate and warm-temperate regions; 3 species in Australia, 1 introduced.
Young shoots of most species are edible when boiled for a few minutes.