Herbs, shrubs, rarely trees or climbers. Stems often with swollen nodes. Leaves usually alternate, simple; stipules united forming a sheath around the stem (ochrea). Ochreae membranous, scarious, hyaline, fimbriate, lacerate, ciliate or sometimes entire at the mouth. Inflorescence of various types, basically a cyme often disposed in spikes, heads or panicles. Flowers bisexual, rarely unisexual, actinomorphic. Perianth biseriate, composed of 3, 4, 5 or 6 tepals which are united below, the inner sometimes enlarged or modified with hooks, spines, wings or tubercles, tepals often persistent, usually enlarged and membranous in fruit. Stamens 4-9(-16), uni or biseriate with nectar secreting glands at the base, pollen grains 3-4, colpate, 3-colporate, pantoporate or triporate. Carpels 2-3, syncarpous, ovary superior, unilocular, ovule 1, seemingly basal; styles 2-4 with capitate or fimbriate stigma. Fruit a biconvex or trigonous nut, often enclosed by the persistent perianth, shining, brown to black. Seed usually with a curved embryo.
A family of 55 genera and possibly over 1150 species, mostly distributed in temperate regions, particularly in the northern hemisphere. Represented in Pakistan by 19 genera and 103 species.