A monk (/mʌŋk/, from Greek: μοναχός, monachos, "single, solitary" and Latin monachus) is a person who practices religious asceticism, living either alone or with any number of other monks. A monk may be a person who decided to dedicate his or her life to serving all other living beings, or to be an ascetic who voluntarily chooses to leave mainstream society and live his or her life in prayer and contemplation. The concept is ancient and can be seen in many religions and in philosophy.
In the Greek language the term can apply to women, but in modern English it is mainly in use for men. The word nun is typically used for female monastics.
Although the term monachos is of Christian origin, in the English language "monk" tends to be used loosely also for both male and female ascetics from other religious or philosophical backgrounds. However, being generic, it is not interchangeable with terms that denote particular kinds of monk, such as cenobite, hermit, anchorite, hesychast, or solitary.
In Eastern Orthodoxy monasticism holds a very special and important place: "Angels are a light for monks, monks are a light for laymen" (St. John Klimakos). Orthodox monastics separate themselves from the world in order to pray unceasingly for the world. They do not, in general, have as their primary purpose the running of social services, but instead are concerned with attaining theosis, or union with God. However, care for the poor and needy has always been an obligation of monasticism, so not all monasteries are "cloistered". The level of contact though will vary from community to community. Hermits, on the other hand, have little or no contact with the outside world.