Definition
In civil law and historical English law, *duplum* means "double." As a legal term of art, it refers to a doubled measure — most commonly the doubling of damages as a penalty or remedy. The phrase *damna in duplo* (damages in double) expresses the core application: a court's award of twice the actual loss suffered, imposed either as punishment or as a statutory remedy.
The term appears principally in the context of Roman civil law, where *duplum* designated the doubled penalty available in certain actions — including the *actio furti manifesti* and related theft actions — and carried over into medieval English legal usage through the influence of canon law and the civilians.
Why It Matters in Research
Researchers encountering *duplum* in historical sources should note that it almost always signals a penal or punitive element rather than simple compensatory recovery. When you see *duplum* in a pleading, statute, or treatise, the question to ask is: double of what? The base measure varies by context — double the value of the thing taken, double the debt, or double a fixed statutory penalty.
The most important English statutory anchor is the Statute of Westminster II (1285), chapter 26, which Burrill cites directly. Researchers working in late thirteenth- and early fourteenth-century English legal materials will encounter *duplum* in connection with that statute. Do not assume that every reference to *duplum* in an English source reflects Roman law doctrine; many are purely statutory invocations of the Westminster framework.
In Roman law sources, *duplum* sits within a structured hierarchy of penalties — *simplum* (single), *duplum* (double), *triplum* (triple), *quadruplum* (fourfold) — that distinguished the severity of remedies across different actions. A researcher moving from English to civilian sources, or vice versa, must be careful not to import the civilian taxonomy into common law materials, where the term was used more loosely and instrumentally.
Cross-corpus alert: *Duplum* will appear in translated or Latin-text editions of Justinian's Corpus Juris Civilis, in the glossators and commentators, and in English Year Books and statutes. The register shifts considerably across these bodies of material, and the specific action or statute generating the *duplum* penalty must always be identified before interpreting any claim or award.
Historical Dictionary Support
Burrill's entry is terse but precise: "Double. Damna in duplo; double damages. Stat. Westm. 2, c. 26." This one-line treatment is consistent with how historical legal dictionaries handled Latin maximally-compressed terms — treating them as self-defining once the Latin is translated. The entry does exactly what it needs to do: it anchors the term to a concrete English statutory reference and gives the operative phrase (*damna in duplo*) that researchers will actually encounter in sources.
What Burrill does not supply — and what no single historical dictionary entry could — is the full Roman law background. The civilian literature treats *duplum* as part of an elaborate remedial typology tied to specific actions and degrees of fault. That framework is not accessible through the common law dictionary tradition and must be pursued in the civilian and canon law sources directly.
Jurisdictional Note
*Duplum* as a live term of art belongs primarily to Roman and civil law jurisdictions and to historical English common law under specific statutory authority. Modern common law jurisdictions use "double damages" or "treble damages" in English without resort to the Latin. Researchers in Louisiana, Quebec, or other mixed civil law jurisdictions may encounter *duplum* in older materials with civilian resonance.