Sheep, a mammal that is closely related to the goat. Sheep, like cattle, are ruminants; that is, they chew a cud. Their stomachs have four chambers for digesting the grass and other plant material they eat. Their hooves are split into two parts, making them cloven-hoofed.

There are both domestic sheep and wild sheep, and there is a great difference in their appearance. Domestic sheep have long tails (which are usually removed at an early age) and, usually, a woolly coat; wild sheep have shorter tails and a coat made up of stiff hairs. Male sheep are called rams; females, ewes. Domestic sheep under one year old are usually called lambs.