( O )
Omne sacramentum debet esse de certa scientia – Every oath ought to be of certain knowledge.
Omnia delicta in aperto leviora sunt – All crimes (committed) in the open are (considered) lighter.
Omnia praesumuntur contra spoliatorem – All things are presumed against a wrongdoer.
Omnis innovatio plus novitate perturbat quam utilitate prodeat – Every innovation disturbs more by its novelty than it benefits by its utility.
Optima legum interpres est consuetudo – The best interpreter of laws is custom.
Optimus interpres rerum est usus – The best interpreter of things is usage.