Deciduous, semi-deciduous or evergreen trees or occasionally shrubs, monoecious. Indumentum, when present, of stellate hairs. Leaves alternate, toothed, lobed or occasionally entire, those of deciduous species often coloured in autumn. Flowers produced before or with new leaves (deciduous spp.). Male flowers in pendulous catkins, often rather sparse; perianth of mostly 5 or 6 narrow, acute sepals, shortly fused at base; stamens 4-6(-12). Female flowers solitary, paired or in small spikes from leaf axils; perianth rudimentary, styles usually 3. Fruit a 1-seeded nut (acorn) maturing in 1 or 2 years, partially enclosed in a cupule of fused or partly fused basal scales.
Many species grown for ornament, occasionally escaping but rarely seriously invasive away from plantations or gardens.