A pen is an enclosure for holding livestock. The term describes types of enclosures that may confine one or many animals. Construction and terminology vary depending on the region of the world, purpose, animal species to be confined, local materials used and tradition. Pen or penning as a verb refers to the act of confining animals in an enclosure.
Pen (enclosure) Wikipedia
In Australia and New Zealand a pen is a small enclosure for livestock (especially sheep or cattle), which is part of a larger construction, e.g. calf pen, forcing pen (or yard) in sheep or cattle yards, or a sweating pen or catching pen in a shearing shed. In Australia, a paddock may encompass a large, fenced grazing area of many acres, not to be confused with the American English use of paddock as interchangeable with corral or pen, describing smaller, confined areas.
In the United States, the term pen usually describes small enclosures for holding sheep, goats, and pigs. A pen for cattle is also sometimes called a corral. Pens may be named by their purpose, such as a holding pen, used for short-term confinement. Groups of pens that are part of a larger complex may be called a stockyard, where a series of pens holds a large number of animals, or a feedlot, which is type of stockyard used to confine animals that are being fattened. A large pen for horses is called a paddock (Eastern USA) or a corral (Western USA), a borrowing from the Spanish language. In some places an exhibition arena may be called a show pen. A small pen for horses (no more than 15–20 feet on any side) is a pen if it lacks any roof or shelter, otherwise it is called a stall and is part of a stable. A large fenced grazing area of many acres is called a pasture, or, in some cases, rangeland.
In British English, a sheep pen is also called a folding, sheepfold or sheepcote. Modern shepherds more commonly use terms such as closing or confinement pen for small sheep pens. Most structures today referred to as sheepfolds are ancient dry stone semicircles. Primitive pens in South Africa are called kraal.