jur

At the heart of Roman society sat one word: jūs — meaning both 'law' and 'right.' To a Roman, these were the same thing: what is lawful is what is rightfully yours. From jūs came jūstus (conforming to law, fair), and from there English drew just (fair) and justice (the state of fairness, and the system that enforces it). When you justify something, you literally 'make it just' — you show it conforms to what is right.

But jūs had a twin idea: swearing. To bind yourself to the law, you took an oath — jūrāre, 'to swear by what is right.' A group sworn in to deliver a verdict became a jury; each sworn member is a juror. If you swore falsely, you committed perjury (per- 'through, falsely' + jūrāre) — a lie across your oath. Conjure began the same way: con- (together) + jūrāre = to bind people by a shared oath, which over centuries drifted into 'to summon by magic spell,' as if commanding spirits under oath.

The most important branch fused two roots. Jūdex, the Roman 'judge,' was built from jūs (law) + dīcere (to speak): a judge is literally 'one who speaks the law.' This jud- form runs through judge, judgement, judicial, judiciary, and judicious (showing good judgement). The same fusion explains jurisdiction — jūris (of law) + dīctiō (a saying) = the power to speak the law over a place. And it explains prejudice: prae- (before) + jūdicium (judgement) = a judgement made before the facts — a pre-judging, hence a bias.

Then comes the dark side of jūs. Put in- ('not, against') in front and you get injūria — a thing done against the law, a wrongdoing. English narrowed it to physical harm: to injure is to do someone wrong, and an injury is the damage. Keep the abstract sense and you get injustice — the absence of what is right.

A family caution: the adjust / adjustment / adjustable / readjust group is long associated with this root but its origin is disputed. Most dictionaries trace it to Old French ajuster, from Latin ad- + juxtā ('near, side by side') — 'to bring near, to fit together' — not from jūs. The link to 'law/right' is likely a later folk-etymology. We keep it here because learners have long grouped it with jur, but treat the connection as uncertain.