Res ipsa loquitur - "The thing speaks for itself." Used in tort law when there is no proof of what caused the harm, but it is most likely only the thing that could have caused the harm.⏎
Sententia quae in rem iudicatam transit, pro veritate habetur - When a definitive sentence is declared, it is considered to be the truth. In the case of a sentence in rem iudicatam (that finally consents to consider a judgement completed), its content will then be the only legally relevant consideration of a fact.⏎
Volenti non fit injuria - "Injury is not done to the willing." Notion that a person cannot bring a claim against another for injury, if said person willingly placed themselves in a situation where they knew injury could result.⏎
Vigilantibus non dormientibus aequitas subvenit - "Equity aids the vigilant, not the sleeping." Concept that if an opposing party unreasonably delays bringing an action, that it is no longer considered just to hear their claim, due to fundamental changes in circumstance brought upon by their delay.⏎
Solve et repete - Respect your obligation first, then you can ask for reimbursement. Used in those situations in which one of the two (or more) parties needs to complete his obligation before being allowed to ask for the opposite obligation to be respected by his counter party. Usually this principle is used in fields and subjects in which a certain general steadiness or uniformity of the system has been considered a relevant value by the legislator. The case is typical of service contracts with repeated obligations (like with gas, water, electricity providers and similars), in which irregularities on one side cannot be balanced if not in a regular situation (i.e., of payments) on the other side. The customer, for example, might be asked to pay regularly the new bill, before contesting the previous one in which he found irregular calculations, and asking for a balancement with newer bills; he thus cannot by himself determine a discount in the next payment.⏎