Annual or perennial herbs, creeping or with taproots, mostly weeds of disturbed ground. Many species are pantropical or almost cosmopolitan in distribution, often by introduction.

Members of the family may be recognised (in 10/14 genera) by their opposite leaves, which are also simple and exstipulate, and condensed, erect, leafless racemose inflorescences (often spikes or clusters) with dry bracts and bracteoles, of minute apetalous flowers, each with a dry, often coloured calyx. The fruit is a utricle (an inflated achene, but see Chapter 39, Cyperaceae), which may, however, dehisce.

Introduced cultivated ornamentals include bachelor's button (Gomphrena globosa), cockscomb (Celosia argentea f. cristata), love-lies-bleeding (Amaranthus sp., see below) and Alternanthera (now tenella var.) bettzickiana.

There are very few climbers in the family and Sericostachys scandens, in the forests of southern Nigeria and Cameroun, is the only ± woody one. It has opposite leaves and large inflorescences, each unit of which is composed of one fertile and two (to three) sterile flowers. These latter develop white feathery hairs as the fruit ripens, and the infructescences are very striking.

Two more species are distinctive by both habit and habitat. Centrostachys aquatica, the only species in its genus and the only aquatic species in the family, has occasionally been collected along the southern border of the Sahara, to where its North African distribution extends. It has grooved floating stems rooting at the lower nodes and bearing opposite leaves, and flower spikes up to 30 cm long.