A vow of silence is a religious vow, usually taken in a monastic context, to maintain silence. Known as Mauna in Hinduism, Jainism, and Buddhism, the practice is integral to Christian and Islamic traditions as well. Apart from that it is also followed as a spiritual practice.
Pythagoras imposed a strict rule of silence on his disciples; the Vestal virgins also were bound to severe silence for long years. Many similar examples could be quoted.
Spiritual silence may be viewed from a threefold standpoint:
Religious orders such as the Benedictines have insisted on this as one of the essential rules of their institutes.
In monasteries of many orders there are special places, called the "Regular Places" (church, refectory, dormitory etc.) and particular times, especially the night hours, termed the "Great Silence", wherein speaking is more strictly prohibited.
Outside these places and times there are usually accorded "recreations" during which conversation is permitted, governed by rules of charity and moderation, though useless and idle words are universally forbidden in all times and places. Of course in active orders the members speak according to the needs of their various duties.
It was perhaps the Cistercian Order alone that admitted no relaxation from the strict rule of silence, which severity is still maintained amongst the Reformed Cistercians (Trappists) though other contemplative Orders (Carthusians, Carmelites, Camaldolese etc.) are much more strict on this point than those engaged in active works.
In order to avoid the necessity of speaking, many orders (Cistercians, Dominicans, Discalced Carmelites etc.) have a certain number of signs, by means of which the religious may have a limited communication with each other for the necessities that are unavoidable.
In the Indian religions religious silence is called Mauna and the name for a sage, muni (see, for example Sakyamuni) literally means 'silent one'.
Obrecht, Edmond (1913). "Silence". Catholic Encyclopedia. New York: Robert Appleton Company.