"Maha Nikaya" (literal translation: Great Collection) refers to one of the two principal sects of modern Thai Buddhism. The other principle sect is Dhammayuttika Nikaya. Generally, the Dahmayutti Nikaya sect of Theravada Buddhism is more strict than the Maha Nikaya sect.
The identification of the Maha Nikaya as a single, discrete, entity is an innovation of the Thai state. After the founding of the Dhammayuttika Nikaya by the then-monk Prince Mongkut in 1833, decades later all recognized monks not ordained in the Dhammayuttika order were considered to be part of the 'maha nikaya', the 'great collection' of those outside the new Dhammayuttika fraternity. As such, most monks in Thailand belong to the Maha Nikaya more or less by default; the order itself did not originally establish any particular practices or views that characterized those adhering to its lineage. There were in reality hundreds of different Nikayas throughout the Thai areas that were lumped together as the "Maha Nikaya".
In Cambodia, a similar situation exists; the Dhammayuttika Nikaya was imported from Thailand in 1855, and those monks remaining outside the Dhammayuttika order were recognized as being members of the 'Maha Nikaya' (Khmer: មហានិកាយ Mohanikay). A separate supreme patriarch for the Dhammayuttika Nikaya was appointed by King Norodom; the previous national supreme patriarch then became the titular head of the Cambodian Maha Nikaya.
A monk (from Greek: μοναχός, monachos, "single, solitary") 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 life to serve the other living beings or to be an ascetic who voluntarily chooses to leave mainstream society and live his 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. Meanwhile nun is typically used for female monastics.
Although the term monachos ("monk") is of Christian origin, in the English language it tends to be used analogously or loosely also for both male and female ascetics from other religious or philosophical backgrounds.
The term monk is generic and in some religious or philosophical traditions it therefore may be considered interchangeable with other terms such as ascetic. However, being generic, it is not interchangeable with terms that denote particular kinds of monk, such as friar, cenobite, hermit, anchorite, hesychast, solitary.