A general term for ecclesiastical gatherings under hierarchical authority, for the discussion and decision of matters relating to faith, morals, or discipline. It corresponds to the Latin word concilium. The word synodus appears probably for the first time in the so-called "Apostolic canons", while the word concilium was employed in the same meaning by Tertullian more than a century earlier. Synod and council are, therefore, synonymous terms.

When the bishops of the whole world are congregated under the presidency of the pope, the synod is denominated ecumenical or general. It is only to such an assembly that it is lawful to apply the term sancta synodus (see GENERAL COUNCILS). If the bishops of an ecclesiastical province meet under the headship of their metropolitan, the council is termed provincial. When the hierarchs of all the provinces of a nation assemble, the synod is called national, or, under certain circumstances, plenary. The regulations governing provincial and plenary councils are practically the same. In addition to those mentioned, there are other synods that are more difficult of classification, as synods of the East or the West, the synodoi endemousai of Constantinople, and the mixed councils of ecclesiastical and secular dignitaries who assembled together to make regulations for both spiritual and civil matters.

Different from all other councils is the diocesan synod. Other councils are assemblies of bishops who have a definitive vote in the matters under consideration, but in a diocesan synod there is only one voter and only one lawgiver, the bishop of the diocese. This article deals mainly with diocesan synods. In his book "De Synodo Dioecesana" (lib. 1, c. i) Benedict XIV thus defines a diocesan synod: "A lawful assembly convoked by the bishop, in which he gathers together the priests and clerics of his diocese and all others who are bound to attend it, for the purpose of doing and deliberating concerning what belongs to the pastoral care." The Council of Trent (Sess. XXIV, c. ii, "De ref.") required that a diocesan synod be held once a year. This law is still in force, but a mild interpretation, introduced by custom, has been tacitly sanctioned by the Holy See. Usually, the date for holding the synod should be announced on the Feast of the Epiphany. A month before the opening the decree of convocation should be affixed to the cathedral doors, and it should be published on three successive Sundays in parish churches. When two dioceses are united under one bishop, the synod should be celebrated alternately in the cathedral of each such diocese. It belongs to the bishop to convoke the diocesan synod whether he be consecrated as yet or not. An archbishop, however, who has not yet received the pallium, has not the same right. Vicars-general can assemble a synod only in virtue of a special mandate of the bishop. When a diocese is vacant, the vicar capitular can and should hold a diocesan synod if a year has elapsed since the celebration of the last once. Ordinarily, the convocation of a synod should take place after the episcopal visitation of the diocese, as the bishop can then be better guided in forming his statutes. When, however, the visitation has been neglected for years, it is considered more advisable to hold the synod first. As the bishop is the only law-giver at a synod, it belongs to him to draw up the various decrees which he may wish to promulgate at its sessions. While he convokes the synod by his own authority and is not required to consult his chapter concerning the convocation or its preparatory acts, yet he must ask the counsel of his chapter or diocesan consultors as to the decrees he desires to enact, though he is not bound to follow their advice. The bishop is exhorted, in the formation of his decrees, to hold private conferences with the prudent, learned, and pious clerics of his diocese, and then to consult his chapter on the proposed statutes thus formed (S. C. C., 26 Nov., 1689). Only in this way does the bishop deliberate with the clergy of his diocese at a synod, and though the finished decrees will receive all their authority from him, yet it is consonant with the mind of the Church that, in the formation of the statutes, the opinion of the clergy be heard and considered. Summonses to a diocesan synod should be given to the vicar-general, the members of the cathedral chapter, holders of benefices, and all others who have care of souls. If there is a custom to that effect, all the clergy of the diocese may be summoned. Regulars who have care of souls are obliged to attend a synod. Their superiors are not, however, obliged to attend, unless they personally act as parish priests or curates. The bishop has power to punish with censures all those legitimately summoned who fail to attend. Laymen may also be invited by the bishop to be present at a synod if there is a custom to that effect, but under no circumstances can they acquire a right to such summons.

At the synod the decrees determined on by the bishop are promulgated, and a period of two months is allowed for having recourse against them to the bishop or the Holy See. All the clergy and laity of the diocese are bound by these decrees, and it is not necessary for the bishop to send his statutes to Rome for revision before publication. Exempt regulars are bound to observe diocesan decrees in all things which concern the sacred canons, the Constitutions of popes and councils, and the decrees of the Sacred Roman Congregations. The bishop may not force his clergy to buy printed copies of the diocesan statutes (S. C. C., 14 Dec., 1658). During the synod the appointment is made of synodal examiners. To the former duties of these officials has been added by the "Maxima Cura" of Pius X (20 Aug., 1910) that of being associated with the bishop in drawing up the decree for the administrative removal of parish priests. By the same papal Constitution, parochial consultors, who are to be assessors in case of recourse against a decree of removal, are also to be chosen by the synod from among the parish priests. Synodal witnesses are likewise chosen at some synods, whose main duty it is to help in the framing of deliberative questions or to report at the following synod what has been the effect of the degrees promulgated at the last assembly, or to suggest new ones. Synodal judges are also to be chosen, though they are rarely now employed. Their office is to expedite such causes as may be committed to their judgment outside Rome by the Holy See. These judges should be at least four in number in every diocese, and their names must be forwarded to Rome as soon as selected. The subject-matter of the decrees framed at a diocesan synod should concern only the preservation of faith or discipline. Under no circumstances may such a synod define any new article of faith or decide any doctrinal point in dispute between Catholic theologians or frame statutes contrary to the common canon law of the Church.

For synods in general use see bibliography of article COUNCILS, GENERAL. The best work on diocesan synods is that of BENEDICT XIV, De Synodo Dioecesana. BOUIX treats of these synods in De Episcopo, II (3rd ed., Parish, 1883); FERRARIS, Bibliotheca Canonica, II (Rome, 1891), s. v. Concilium, art. 3; in TAUNTON, The Law of the Church (London, 1906), s.v.; HEFELE, Councils of the Church, ed. CLARK (Edinburgh, 1871—-), and new French translation by LECLERCQ (Parish, 1907—-).

W.H.W. FANNING