Trees or shrubs, usually deciduous, monoecious, rarely dioecious; branchlets solid or with partitioned pith. Stipules absent. Leaves alternate, rarely opposite, odd- or even-pinnate; leaflets with glandular scales, often aromatic. Flowers unisexual, arranged in catkins, produced on the previous or current year’s growth. Catkins solitary or clustered, pendulous or erect, elongate. Male flowers subtended by an entire or 3-lobed bract, bracteoles 2 or absent; perianth 2–6-lobed or absent; stamens 3–50, filaments short. Female flowers subtended by an entire or 3-lobed bract, bracteoles 2–3 or absent; perianth 4-lobed or absent; ovary inferior, unilocular at apex, carpels usually 2; style 1, stigmas 2. Fruit a large nut, sometimes fleshy and drupe-like, dehiscent or indehiscent, or rarely a samara; seed 1, lacking endosperm.
Nine genera and c. 60 species mainly from temperate and subtropical regions in the Northern Hemisphere, includes walnuts (Juglans) and pecans (Carya Nutt.), only the former is recorded as naturalised in Australia.