In canon law, a canon designates some law promulgated by a synod, an ecumenical council, or an individual bishop. The word "canon" comes from the Greek kanon, which in its original usage denoted a straight rod that was later the instrument used by architects and artificers as a measuring stick for making straight lines. Kanon eventually came to mean a rule or norm, so that when the first ecumenical council—Nicaea I—was held in 325, kanon started to obtain the restricted juridical denotation of a law promulgated by a synod or ecumenical council, as well as that of an individual bishop. Greek kanon / κανών, Arabic qānūn / قانون, Hebrew kaneh / קנה, "straight"; a rule, code, standard, or measure; the root meaning in all these languages is "reed" (cf. the Romance-language ancestors of the English word "cane"). A kanon was the instrument used by architects and artificers for making straight lines. Legal history of the Catholic Church Some writers think that the Church preferred the word canon to law, as the latter had a harsh meaning for the faithful in the times of persecution. The early Fathers use canon as equivalent to the rule of faith, or for some formula expressing a binding obligation on Christians. Bickell declares that for the first three hundred years, canon is scarcely ever found for a separate and special decree of the Church; rather does it designate the rule of faith in general. He appeals to the fact that the plural form of the word is seldom used in the earliest Christian writers. With the fourth century began the use of canon for a disciplinary decree, owing to its employment in this sense by the First Council of Nicea (325 A.D.). The Cassinese editors of Ferraris say that in the first ages of the Church many disciplinary regulations were not required, and hence it was scarcely necessary to discriminate decrees into dogmatic and disciplinary, as the faithful classed both under the obligation to observe the general rule of faith.