Brethren (ἀδελφοί), one of the common appellations of Christians. It occurs frequently in the N.T., and was current at the date of the apostolical epistles. Subsequently it became a title of respect and affection by which the baptized, or faithful, or complete members of the Church were distinguished from the catechumens. They were accosted or described by other titles, such as "the enlightened," "the initiated," "the perfect," "elect," "beloved," "sons of God," "beloved in Christ," etc. SEE BROTHER.