Monk, translated as monk in English, refers to people who enter monasteries to practice after the formation of the Christian convent system. They must swear to be absolutely beautiful, never get married, serve God, live in a monastery and study and work every day. Many monasteries have a tradition of penance. Monks often fast and sleep on the cold ground at night to atone for their sins. The strict monastery system also prohibits monks from going out to contact with the outside world, or even talking between monks, and only allows one or two necessary whispers or gestures.

Monks are different from later dervishes. The appearance of dervish is relatively late, and the most famous ones are Franciscans and Dominicans. Although they also live a single life away from home and serve God, they do not live in monasteries, but preach among the poor. They have no property and live the poorest life on the charity of believers. They are generally called "joining forces". Many missionaries are enthusiastic missionaries. For example, Matteo Ricci, who entered China, was a Jesuit. However, monks who live in temples all their lives do not undertake missionary work.