Find accurate definitions of over 5,000 Catholic terms and phrases (including abbreviations). Based on Fr. John Hardon's Modern Catholic Dictionary, © Eternal Life. Used with permission.
A long-standing practice that takes on the force of law. No custom is ever valid that contradicts a divine law, whether natural or positive, nor does a custom abrogate ecclesiastical law unless it is reasonable and has been legitimately in practice over a period of forty full years. Where the ecclesiastical law explicitly forbids contrary customs, the latter can be valid only if they are reasonable and in legitimate existence for at least a century or from time immemorial.