Definition
In Roman and civil law, *hostis* (plural: *hostes*) denotes a public enemy — specifically, a person or people against whom formal, open war has been declared by a sovereign authority. The term carries a technical weight that distinguishes it from other Latin words for adversary or foe: a *hostis* is an enemy of the state in the fullest legal sense, recognized as a belligerent under the law of nations, not merely a private antagonist or criminal.
The word carries two distinct senses that surface in legal and historical sources:
1. PUBLIC ENEMY (Roman and Civil Law Usage): The *hostis* is an enemy recognized by formal proclamation of war — a foreign power or its subjects standing in open, declared hostility to the Roman state or, in later usage, to a sovereign nation. This formal recognition had legal consequences: the laws of war applied, captives could be held as prisoners of war, and certain protections and duties attached that would not apply to common criminals or pirates.
2. MILITARY HOST OR ARMY (Medieval Latin Usage): In the laws and records of feudal Europe, *hostis* or its Latinized French derivative (from *hoste*) came to mean the host itself — the assembled military force called to service. This sense is entirely distinct from the first and appears in feudal charters, conciliar proceedings, and treatises on feudal tenure, where rendering service in the *hostis* was a core obligation of the feudal compact.
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Common Language
Modern common usage (Wiktionary): *Hostis* is not a current English word. In modern Romance languages descended from Latin, cognates such as the French *hôte* (host, guest) and the English *host* derive from the same root but have shed all military or enemy connotation.
Historical common usage (Webster's 1913): The English word *host*, meaning an army or multitude, and also a person who receives guests, both descend from Latin *hostis* and its derivative *hospes*. By the medieval period these meanings had diverged so sharply as to be felt as separate words.
The gap matters for legal research: English-language documents using *host* in a military sense (a feudal host, the host of an army) and Latin documents using *hostis* in the same feudal context are drawing on the same word root but in its military-host meaning — entirely different from the public-enemy sense that dominates classical Roman legal texts. Researchers conflating the two senses of *hostis* will misread either Roman law materials or medieval feudal records.
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Common Confusion
HOSTIS vs. INIMICUS vs. PERDUELLIS: Classical Latin distinguished carefully among these. *Inimicus* was a personal enemy — someone with whom one had a private quarrel. *Perduellis* was the older, more emphatic term for a traitor or enemy in arms against the state, carrying the gravest connotation of treasonous hostility. *Hostis* occupied middle ground: by the classical period it had come to mean the foreign public enemy recognized under the law of nations, distinct from the internal traitor (*perduellis*) and the merely personal adversary (*inimicus*). Cicero and other classical sources note this evolution explicitly. Legal texts deploying any of these terms require the researcher to attend to which word is used and in what period — the distinctions collapse in later Latin but are operative in classical sources.
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Why It Matters in Research
The dual meaning of *hostis* is a persistent trap in historical legal research. A researcher working in Roman law sources will encounter *hostis* as the technical term for a public enemy — a status with defined legal consequences under the *jus gentium* and the laws of war. A researcher working in medieval feudal records, canonical proceedings, or Carolingian legislation will encounter *hostis* meaning the military levy or army itself, reflecting the word's journey through Vulgar Latin and Old French.
Burrill flags the medieval usage and directs readers to Spelman and the *Feudorum Libri*, the standard reference for feudal tenure obligations. Researchers using Burrill to interpret a term in a Roman or civil law context should not allow the medieval gloss to contaminate that reading, and vice versa.
The evolution also touches the law of nations and early international law. Treatises in the *jus gentium* tradition — Grotius, Vattel, and their predecessors — rely on the *hostis* / *inimicus* distinction to demarcate the boundary between war (governed by international law) and crime or insurrection (governed by domestic law). Identifying whether a belligerent is a *hostis justus* (a lawful public enemy) determined whether the laws of war applied, whether prisoners were entitled to quarter, and whether captured property passed by right of war. That doctrinal framework remains influential in the history of international humanitarian law.
In the Law Mind corpus, *hostis* is most likely to appear in: civil law commentaries, treatises on the law of nations, feudal tenure materials, and ecclesiastical council proceedings. The reader should determine from context which sense governs before proceeding.
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Historical Dictionary Support
Burrill provides the core dual entry: public enemy (Roman/civil law sense) and military host (medieval/feudal sense), citing Spelman and the *Feudorum Libri* for the latter. This is accurate and adequately sourced for a mid-nineteenth century law dictionary.
What Burrill does not address is the classical internal distinction between *hostis*, *inimicus*, and *perduellis* — a distinction operative in sources that predate the medieval feudal usage and essential for reading Roman republican and classical texts accurately. The Latin dictionary material supplied here fills that gap: *hostis* began as a word for foreigner or stranger (*hospes* shares the root) and only over time acquired its dominant sense of public enemy, displacing the older *perduellis* for most purposes. This etymological drift explains why medieval scribes could use the word for a military gathering without any sense of contradiction — the stranger-guest-army cluster of meanings was always latent in the term.
No major divergence exists across available sources on the core definition. The only risk is the researcher who relies on a single-sense gloss.
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Jurisdictional Note
*Hostis* as a technical legal term is a feature of Roman law, the civil law tradition, medieval feudal systems, and early international law. It has no operative role in modern domestic common law jurisdictions. Its significance in current research is historical and comparative.
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