A monk is bound by vows, and it is the vows rather than any ordination that constitute the office, a point that distinguishes the monastic life from the priesthood.
Bound by profession
In the Benedictine tradition the vows are of stability, of obedience, and of conversion of life, which encompasses celibacy and the renunciation of private property, and a man becomes a monk by professing them within a community, not by being ordained, so that many monks are not priests and the two states are distinct. The monk life is ordered around the round of communal prayer, the work of the community, and the seeking of God within the enclosure, under a rule and an abbot.
A wide and old ideal
Entry is by a period of testing, the novitiate, followed by profession, first for a term and then for life, so the office is entered gradually and by free commitment. The monastic ideal is far older and wider than Christianity: the Buddhist bhikkhu bound by the monastic code, the Hindu and Jain renunciant, and the monks of other traditions represent the same fundamental impulse, the withdrawal from ordinary life under vows for the sake of a spiritual end. What the Christian monk shares with these is the constitution of the office by renunciation and vow rather than by any sacramental order, the monk being first of all one who has professed a way of life.