Sheep have a vertical cleft and narrow snout completely covered with short hair except on the margins of the nostrils and lips. The genus Ovis is characterized by the presence of glands situated in a shallow depression in the lacrimal bone, the groin area, and between the two main toes of the foot. These glands secrete a clear semi-fluid substance that gives domestic sheep their characteristic smell. The skulls of domesticated sheep differ from those of wild sheep in that the eye socket and brain case are reduced. Selection for economically important traits has produced domestic sheep with or without wool, horns, and external ears.
Coloration ranges from milky white to dark brown and black.
There is considerable diversity among the over 200 distinct breeds of sheep. In general, sheep feed mainly on grasses while in pastures and can be fed a wide variety of hays and oats. Grazing sheep ingest a large amount of food in a short time, then retire to rest and rechew the ingested matter. Sheep spend their day alternating between these periods of grazing and ruminating. Ovis aries has a large and complex stomach which is able to digest highly fibrous foods that can not be digested by many other animals.