Cage, the word that refers to a structure that confines living beings, has numerous synonyms, each of which evokes a slightly different image of the protective or restrictive shelter. For instance, "enclosure" implies a guarded space that is designed to prevent animals from escaping. "Pen" suggests a smaller area that is used to keep animals for a short time, while "coop" is used to describe poultry housed in a small, enclosed space. "Aviary" or "birdcage" refers to a cage specifically designed to accommodate birds, while "corral" implies a larger area that is generally used to contain beasts such as horses and cows.