Plants annual or perennial herbs, monoecious or species dioecious, glabrous or with short and gland-like or multicellular hairs.Leaves alternate, long-petiolate; blades entire or sinuate. Inflorescences bascilaly cymose, bracteate, formed of dense to lax axillary clusters ot the upper leafless, varying from more or less touching to not touching forming a spike or panicle or clearly separate clusters. Flowers unisexual; tepals (2-)3-5, free or almost so, those of the female flowers somewhat accrescent in fruit; stamens usually as many as the tepals; free; ovaries with 1 ovule. Fruits dry, indehiscent, irregularly rupturing or circumscissile capsules; seeds usually compressed, black, shining.
Amaranthus includes about 60 species. It is best represented in tropical to warm temperate regions of the world, occurring as casual weeds in cooler, temerate regions.