Herbs, rarely subshrubs, annual or perennial, armed with stinging hairs. Stems often 4-angled. Leaves opposite; stipules often persistent, interpetiolar, lateral, free or connate; leaf blade 3-5(-7)-veined, margin dentate or incised-lobed; cystoliths often punctiform, sometimes short botuliform. Inflorescences in axillary pairs; glomerules forming spikes, racemes, panicles, or rarely capitula, unisexual (plants monoecious or dioecious) or androgynous. Male flowers: perianth lobes 4, imbricate; stamens 4; rudimentary ovary cuplike. Female flowers: perianth lobes 4, free or connate, enlarged in fruit, enclosing achene, strongly unequal, outer 2 (lateral) smaller than inner 2 (dorsal-ventral) lobes. Ovary straight; stigma sessile or on short style, penicillate-capitate. ovule orthotropous. Achene straight, compressed, enclosed by persistent perianth. Seed erect, with scanty endosperm; cotyledons suborbicular, fleshy.

The stem fibers are used to make ropes, the leaves are used as fodder, and the young shoots are used as a seasoning substitute for sorrel.

About 30 species: principally in N and S temperate regions, also in montane areas of tropics; 14 species (three endemic) in China.

(Authors: Chen Jiarui (陈家瑞 Chen Chia-jui); Ib Friis, C. Melanie Wilmot-Dear)