A bhikkhu (monk) is a man who has renounced ordinary society to live a celibate monastic life.
The Buddha dhammawiki founded an order of monks and nuns called the Sangha dhammawiki, to provide the optimal environment to practice the Dhamma dhammawiki and also to have a body of specialists who could transmit that Dhamma dhammawiki.
Monks are expected to have eight simple requisites and to live by the 227 rules of the Vinaya dhammawiki. Someone can become a novice (samanera) while still a boy but must be twenty years old or over to be a fully ordained monk (upasampadà). If he loses interest in the monastic life, a monk can leave at any time. The most characteristic features of Buddhists monks are their yellow robes, their shaven heads and their calm, smiling demeanour.