The acorn is the oak nut. It usually contains a single and rarely two seeds in a tough, leathery shell in a cup-shaped cupule.

Acorns may vary from 1–6 cm in length. They need 6 and 24 months to mature.

Acorns are one of the most important wildlife foods in areas where oaks are abundant. Acorns along with other nuts are termed mast.

Birds like Jay, pigeon and ducks, as well as mammals like mice, squirrels and rodents feed on acorns.

Acorns are attractive to animals since they are large and rich in nutrients. Proteins, carbohydrates, fat, minerals are present in acorns. Energy given by acorns is high compared to the other nuts and other wild food.

Acorns were a source of food for many cultures around the world. In Korea, an edible jelly and noodles are made from acorns. During the world wars acorns were one of several ingredients of coffee.

Acorns were a traditional food of Native Americans
especially the Californians native Americans.

Unlike many other plant foods, acorns may be stored for a long time before being used. Native Americans collect and store acorns for two years when their production is good.