Definition
Priso is an obsolete Latin and Law French term from medieval English law denoting a prisoner or captive. Two related meanings appear in the historical record:
1. A prisoner of war — a person taken captive during armed conflict.
2. An imprisoned offender — a person held in confinement by legal authority, sometimes rendered as prisones to denote prisoners generally.
The term is archaic and carries no operative legal meaning in modern law. It survives only in historical legal texts, Year Books, and treatises such as Bracton and Fleta.
Common Language
Modern common usage (Wiktionary): No entry. The term does not appear in contemporary English usage.
Historical common usage (Webster's 1913): No entry. The term had already passed out of common use before the modern English period.
The word is a Latin and Law French relic. Its English descendant, "prisoner," carries the same general meaning in both common and legal usage today, but priso itself is encountered only in medieval sources and the learned dictionaries that compiled them.
Common Confusion
Priso is sometimes confused with prise (the act of taking or seizure) and with prisona (prison, the place of confinement). These are related but distinct concepts: priso denotes the person captured or confined; prisona denotes the institution or place; and prise denotes the act of taking. Researchers encountering any of these terms in manuscript sources should verify which form appears, as copyists and editors occasionally conflated them.
Why It Matters in Research
Researchers will encounter priso almost exclusively in:
— Bracton's De Legibus et Consuetudinibus Angliae and Fleta, where the term appears in discussions of captivity, ransom, and the legal status of persons taken in war.
— Year Books and plea rolls from the twelfth through fourteenth centuries.
— Glossaries and Latin-language indices in early English legal treatises.
The term is not a live research target in modern doctrine. Its research value is philological and historical: understanding it clarifies passages in primary medieval sources that bear on the law of war, the status of enemy combatants, and the early development of imprisonment as a legal institution.
One trap in historical sources: prisones (the plural form cited by Bracton) was used broadly to describe all imprisoned persons, not only prisoners of war. Context determines which meaning applies. Black's Law Dictionary collapses this to the war-captive sense alone; Burrill's is more complete in recording both meanings.
Historical Dictionary Support
Black's and Burrill's agree that priso denotes a prisoner taken in war, but Burrill's is the more thorough source. Burrill traces the derivation through Law French (prison, from prise, meaning "taken"), cites Spelman's Glossarium Archaiologicum for the war-captive sense, and adds the broader meaning of imprisoned offender drawn from Bracton. Burrill also supplies the prisones vero, sic imprisonati construction from Bracton, which is the most substantive primary-source support for the broader sense.
Black's entry, by contrast, is minimal — a single sentence limited to the war-captive meaning. Researchers relying solely on Black's will miss the broader institutional sense of the term as it appears in Bracton.
Neither source discusses the relationship between priso and the development of the common law of imprisonment or the legal status of enemy captives in any depth. For those lines of inquiry, Bracton and Fleta must be consulted directly.
Jurisdictional Note
Priso is a term of medieval English legal Latin with no analog in civil law or continental legal systems as a term of art. It does not appear in Scottish, Irish, or American legal sources in operative use.