Deciduous or evergreen trees or shrubs. Leaves usually dentate, sinuate or pinnately lobed, rarely entire. Flowers green, inconspicuous. Staminate flowers in drooping catkins; bracts minute, soon deciduous; perianth 4-7-lobed; stamens 4-12, usually with no rudiment of an ovary. Pistillate flowers few, sessile on a short or long rhachis, each enclosed by an involucre of imbricated concrescent scales; perianth urceolate, 6-lobed or -dentate, with tube adherent to ovary; ovary usually 3-celled, with 2 ovules in each cell; styles 3, rarely 4-5, erect or recurved; stigmas minute on the flat inner surface of style; rudimentary stamens sometimes present. Fruit an acorn, solitary or in small groups, composed of a large nut (“gland”) and a cupule; gland 1-celled, 1-seeded, generally much longer than cupule; cupule mostly with imbricated, unarmed or somewhat prickly scales. Seeds with thick and large cotyledons. Germination hypogaeous.