Annual or perennial herbs, rarely undershrubs. Leaves usually opposite, rarely alternate or fasciculate, simple, often connate at the base, sessile or subsessile, entire; stipules interpetiolar, silvery scarious, rarely absent. Inflorescence an axillary or terminal cymose head or cluster, flowers rarely solitary terminal. Flowers minute, bisexual, actinomorphic, often perigynous, green or white; bracteate, bracts mostly scarious. Sepals 5, rarely 4, imbricate, persistent. Petals 5, rarely 4, or absent, tree, small, usually subulate-filiform. Stamens 2-5, (rarely more), alternate with petals, usually antisepalous, filaments short, free or connate at the base into a ring; anthers dithecous, dehiscence longitudinal. Carpels 1-3, syncarpous, ovary sessile, rarely stipitate, unilocular, usually one ovuled, rarely 2-4 -ovuled, placentation basal, rarely free central, ovule amphitropous or semi-anatropous, pendulous or erect; style 1, terminal, 2-3 fid, rarely 2, distinct. Fruit indehiscent, one seeded utricle or nut enclosed by persistent clayx. Seed globose to subglobose, reniform or lenticular, endosperm copious or scanty, embryo annular, curved or straight.
This family was previously included in the Caryophyllaceae from which it differs in its perigynous flowers, small subulate-filiform petals (regarded as staminodes by some authorities), basal placentation and indehiscent one seeded utricle or nut enclosed by persistent calyx.