Boma (enclosure) in the context of Christian de Bonchamps

A pen is a fenced/walled open-air enclosure for holding land animals in captivity, typically for livestock but may also be used for holding other domesticated animals such as pets that are unwanted inside buildings. 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.

Similar terms are kraal, boma, and corrals. Encyclopædia Britannica notes usage of the term "kraal" for elephant corrals in India, Sri Lanka, and Thailand.

Kraal (also spelled craal or kraul) is an Afrikaans and Dutch word, also used in South African English, for an enclosure for cattle or other livestock, located within a Southern African settlement or village surrounded by a fence of thorn-bush branches, a palisade, mud wall, or other fencing, roughly circular in form. It is similar to a boma in eastern or central Africa.

In Curaçao, another former Dutch colony, the enclosure was called "koraal" which means coral and which in Papiamentu is translated "kura", a word still in use today for any enclosed terrain, like a garden.