'Lex' is Latin for one sense of the English term, law. In the Canon Law of the Catholic Church, lex refers to law which has been formulated in written form and promulgated by competent authority. While this is the usual sense of "law" in modern legal systems, the legal system of the Catholic Church includes another form of law, ius, which refers to the oral teachings, practices, customs, theological understandings of liturgy and liturgical practices generally prior to the Council of Nicea in 325 a.d., when written legislation became the normative means of communicating Church law.