Definition
In Roman law, an heir entitled to receive one-twelfth (uncia) of a deceased person's estate or inheritance. The term refers to a specific fractional heir — one whose designated share of an estate corresponds to a single uncia, the smallest standard unit in the Roman duodecimal system of apportionment used to divide inheritances.
Roman estates were conceptually divided into twelve equal parts (unciae), and a testator could designate multiple heirs by assigning each a fixed fraction of those twelve parts. An unciarius heres held the minimum fractional entitlement: one part in twelve, or roughly 8.3% of the whole estate.
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Common Confusion
The corrupted spelling "Hjbres" in the Black's 2nd Edition Supplemental entry is a transcription or typesetting error for "Heres." Researchers who encounter this entry in its original form should not treat "Hjbres" as an alternate legal term or a distinct concept. It is the same word: heres, Latin for heir.
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Why It Matters in Research
This term surfaces almost exclusively in Roman law sources and their descendants — civil law treatises, civilian commentaries, and historical scholarship on succession law. Researchers should understand several things before working with it:
**Fractional heir system as a whole.** The unciarius heres makes no sense in isolation. It belongs to a larger Roman taxonomy of fractional heirs keyed to the twelve-uncia scale: a semissarius heres received one-half (six unciae), a quadrantarius heres received one-quarter (three unciae), and so on down to the unciarius at the bottom. Any research involving this term should be conducted alongside the full spectrum of fractional designations.
**Limited corpus presence.** Because the term is pure Roman law terminology, it will appear in Law Mind sources primarily in historical legal dictionaries, Roman law treatises, and civil law commentaries. Do not expect to find it in common law case reporters or Anglo-American statutory material. Researchers working in civilian inheritance law traditions — particularly those of Louisiana, Quebec, or jurisdictions with Roman-Dutch heritage — may encounter derivative concepts, though the Latin terminology itself is rarely carried forward intact.
**Spelling instability in historical sources.** The second word appears in Black's 2nd Edition Supplemental as "Hjbres" — almost certainly a typographical corruption of "Heres" (the standard Latin for "heir"). Researchers searching historical databases should query both spellings, as OCR errors and compositor mistakes in early legal dictionaries are common and can obscure otherwise straightforward terms. The authoritative form is unciarius heres.
**Calvin's authority.** Black's 2nd Edition cites "Calvin" as the source — a reference to Johannes Calvinus (Johann Kahl), whose Lexicon Juridicum (first published 1600, with later editions through the early 18th century) was a standard reference for Roman and civil law terminology. Researchers seeking fuller treatment of this term should consult editions of the Lexicon Juridicum directly.
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Historical Dictionary Support
Black's Law Dictionary (2nd Ed., Supplemental) provides the only entry identified in the Law Mind historical dictionary corpus for this term. The entry is brief — defining the unciarius heres as "an heir to one-twelfth of an estate or inheritance" — and attributes the definition to Calvin (Calvinus, Lexicon Juridicum).
No elaboration on the procedural context, the method of calculating shares when heirs exceeded or failed to fill the twelve unciae, or the consequences of partial designation is offered. Historical sources on Roman succession law (Justinian's Institutes and Digest, Gaius's Institutes) supply the fuller framework that Black's entry presupposes but does not state. The Law Mind corpus's historical dictionaries do not diverge from one another on this term — the absence of competing entries simply reflects how rarely this granular Roman terminology was reproduced in Anglo-American legal reference works.
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