Ordination. The concept of a ministry within the Christian community set apart to guide and serve it dates from the New Testament itself, where already we find clear references to the laying on of hands with prayer for those being so set apart (e.g., Acts 6 and 13). Even gradations within the ministry seem to be recognized in the New Testament, although this is less clear. Certainly deacons appear to have been seen as a different order from that of presbyters. The difference between presbyters (presbyteroi) and bishops (episcopoi) is more obscure and has been for long controversial. By the middle of the 3rd century various gradations had come to be apparently well recognized, for at Rome there were not only a bishop and many presbyters, but deacons, sub-deacons, acolytes, exorcists, readers, and porters. Not till much later, however, did the Roman Catholic Church come to recognize four "minor" orders, namely (in ascending order), porter, reader, exorcist, and acolyte, and three "major" orders, sub-deacon, deacon, and priest. Duns Scotus held a curious view that would surely have few supporters today, namely, that there are nine orders (the seven mentioned plus the tonsure, which all clerics receive as a preliminary ceremony to admission to the clergy, and the episcopate, making nine in all): a theory he defends on the ground that it corresponds to the nine orders of angels in heaven. Thomas Aquinas argues with more theological appositeness that all order to the Sacred Ministry is ordered to the Eucharist, from the lowliest (porter) onward, so that there can be no order sacramentally higher than that of the priesthood; therefore the episcopate is merely the plenitude of the priesthood. A further distinction must be noted. Order in the Sacred Ministry is from one standpoint sacramental, i.e., it relates to the administration of the Church's sacraments, which is surely its essential nature if the Church is what the Church purports to be. It has also, however, administrative and jurisdictional implications. The notion that presbyters (priests) should be organized with one of their number superintending and guiding them is an ancient and very defensible one, since plainly the clergy stand as much in need of fatherly care as do the rest of the People of God. In Catholic tradition, at any rate, only bishops can ordain other priests, and they are therefore essential to the continuity of the Church's ministry. In Protestant tradition the laying on of hands is very widely used as part of the ordination ceremony, although the function of the Protestant ministry is differently conceived.

Geddes MacGregor, Dictionary of Religion and Philosophy, New York: Paragon House, 1989

ordination

Buddhist ordination is a voluntary act and need not be undertaken for life. monks and nuns are free to disrobe and return to lay life at any time if they wish, and in certain countries it has become the custom for males to spend a short time in a monastery (see temporary ordination). In the early days of the Buddha's teaching ministry those who wanted to follow him were admitted simply with the words ‘Come, monk’ (ehi bhikkhu) but a more formal ceremony was soon established. Although there is now much regional variation, the normal pattern in Theravāda countries is for the aspirant to be admitted first as a novice (śrāmaṇera), and then later as a fully fledged monk (bhikṣu) or nun (bhikṣunī). The former is known as the lower ordination (pravrajyā) and the latter as the higher ordination (upasampadā). In the former, the novice repeats three times the formula of the Three Refuges (triśaraṇa) and undertakes the Ten Precepts (daśa-śīla). He/she is then assigned an instructor (ācārya) and a preceptor (upādhyāya). The head is shaved and the novice is presented with three robes (cīvara) and a begging-bowl (piṇḍa-pātra). At the higher ordination the novice become a full member of the Saṃgha and is obliged to follow the rules of the monastic code (Prātimokṣa). Both forms of ordination require a quorum of five ordained monks or nuns with a minimum of ten years in the Order. In Mahāyāna countries there is sometimes a third ordination known as the ‘Bodhisattva ordination’ in the course of which the Bodhisattva vow (pranidhāna) is additionally taken.

A Dictionary of Buddhism, Oxford University Press, 2003, 2004 (which is available in electronic version from answer.com)