christopherzilla please make an acorn emote. The acorn, or oak nut, is the nut of the oaks and their close relatives (genera Quercus and Lithocarpus, in the family Fagaceae). It usually contains a single seed (rarely two seeds), enclosed in a tough, leathery shell, and borne in a cup-shaped cupule. Acorns vary from 1–6 cm long and 0.8–4 cm broad. Acorns take between about 6 and 24 months (depending on the species) to mature; see List of Quercus species for details of oak classification, in which acorn morphology and phenology are important factors.