Quo in Legal Language: Quid Pro Quo, Quo Warranto and More

Legal systems that draw on Roman and Roman-Dutch law, including the South African legal system, retain a working vocabulary of Latin terms. Several of the most persistent of these are built on the word quo. This page sets out what the main terms mean and the kind of legal context in which each one typically appears.

Quid pro quo

Quid pro quo means 'something for something'. In contract law it relates closely to the idea of consideration: the principle that for an agreement to be enforceable, each party generally needs to give or promise something of value in exchange for what they receive. The phrase is also used more loosely outside strict legal drafting, in discussions of any exchange where one party expects something back in return for what they give.

Outside contract law, quid pro quo is sometimes used in employment and administrative contexts to describe an improper exchange, where a benefit is offered or withheld in return for a decision or action that should not be subject to bargaining. In these cases the phrase is used critically, to flag an exchange as inappropriate rather than as a normal, lawful bargain.

Quo warranto

Quo warranto means 'by what authority'. Historically it was a specific legal procedure used to challenge whether an individual or body had the right to hold a public office, franchise or privilege they were exercising. Although the original procedure has largely been replaced or absorbed into modern administrative and constitutional remedies, the underlying question it represents, by what authority is a power being exercised, remains a core concern of constitutional and administrative law. Courts reviewing whether an official, board or institution has acted within its lawful powers are, in substance, asking a quo warranto question even if that exact term is not used in the judgment.

Terminus a quo and terminus ad quem

These two paired terms describe the start and end points of a defined period, most often a limitation period or deadline. The terminus a quo is the point in time from which a period begins to run, for example the date on which a cause of action arises. The terminus ad quem is the point in time by which something must be done, such as the final date for filing a claim or an appeal. Legal arguments about whether a claim was brought in time frequently turn on correctly identifying these two points.

Why these terms persist

Latin legal terms survive partly because they are precise and internationally recognised across legal systems with shared Roman law roots, and partly because changing settled terminology in statutes, case law and textbooks carries its own risk of introducing ambiguity. A term like quid pro quo captures, in three words, a concept that would otherwise need a full sentence to express with the same precision.

Reading these terms correctly

When these phrases appear in a judgment, contract or statute, it is worth pausing on the literal translation rather than treating them as generic legal flavouring. Quid pro quo is specifically about exchange, quo warranto is specifically about authority, and the terminus phrases are specifically about time limits. Keeping the literal meaning in mind makes it easier to follow the legal reasoning that depends on them, and easier to spot when a term is being used loosely rather than in its strict technical sense.