Deciduous or evergreen trees or rarely shrubs, generally with rough fissured bark. Bud scales numerous. Lvs usually short-petiolate, usually toothed to deeply lobed, rarely entire. Fls anemophilous. ♂ fls in slender pendulous catkins; bracts caducous; perianth (4)-6-(7)-lobed; stamens (4)-6-(12). ♀ fls 1-many in catkins; involucre (cupule) surrounding each catkin or individual solitary fl. Ovary 3-(6)-celled; styles short or elongate. Fr. a nut (acorn), usually subglobose to ellipsoid or oblong, invested to varying degrees but never enclosed by woody cup. Involucral scales numerous, imbricate or connate into concentric rings. Seed round in transverse section.