canon
The word canon, derived from the Greek for 'rule', refers to what is accepted as authoritative, usually so transcendently as to be beyond the power of ordinary people to change. People use their canons to adjudicate disputes, though often the canon is itself subject to dispute as well. Perhaps the most famous canon is the Christian Bible, the true contents of which have been argued about since the early Christian centuries. In the Catholic Church, ecclesial law, the communion of saints, and the prayers for Mass are all considered canons.