(Claustrum), a habitation surrounded with walls, and inhabited by canons or religious, &c. In a more general sense, cloister is used for a monastery of religious of either sex. In a more restrained sense, cloister is used for the principal part of a regular monastery, consisting of a square built around; ordinarily between the church, the chapter-house, and the refectory; and over which is the dormitory. The cloisters served for several purposes in the ancient monasteries. Petrus Blesensis observes that it was here the monks held their lectures: the lecture of morality at the north side, next the church; the school on the west, and the chapter on the east; spiritual meditation, &c., being reserved for the church. Lanfranc observes, that the proper use of the cloister was for the monks to meet in, and converse together, at certain hours of the day.

The form of the cloister was square; and it had its name claustrum, from claudo, "I shut or close;" as being inclosed on its four sides with buildings. Hence in architecture, a building is still said to be in form of a cloister, when there are buildings on each of the four sides of the court.