Definition
A Roman law term denoting a fractional division of the as equal to ten unciae, or ten-twelfths of the whole — the equivalent of five-sixths. The as was the fundamental Roman unit of measurement used across inheritance, property, and obligation law, divisible into twelve unciae. The dextans represented the as with two unciae removed (i.e., the sextans, one-sixth, subtracted from the whole), leaving ten parts of twelve.
In practice, the dextans appeared most often in the law of succession and inheritance, where Roman law allocated estates, legacies, and intestate shares by fractional portions of the as. A testator might leave a heir ten-twelfths of an estate, or a legatee might receive a dextans of a particular asset.
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Why It Matters in Research
The dextans is not a living legal term — it will not appear in modern statutes, regulations, or case law. Its relevance to Law Mind corpus researchers is confined to two contexts.
First, it is essential for reading Roman law sources and the civilian tradition that descended from them. Civil law jurisdictions in Europe and Louisiana drew on Roman inheritance and property frameworks, and the fractional vocabulary of the as — uncia, triens, quadrans, semis, bes, dextans, deunx, and others — appears throughout primary sources, civilian treatises, and historical commentaries without translation or explanation. Researchers working in those materials need fluency with this system to parse fractional bequests and property allocations correctly.
Second, the term surfaces in Blackstone's Commentaries (2 Bl. Comm. 462, note m), the single most widely cited reference across the historical legal dictionaries on this point. Blackstone's footnotes on Roman fractional divisions were the primary pathway through which common law lawyers of the eighteenth and nineteenth centuries encountered this vocabulary. Any researcher tracing Blackstone's treatment of property or inheritance who follows his annotations will encounter dextans in this note.
The key trap: the Roman fractional system is counterintuitive to researchers accustomed to decimal fractions. Ten-twelfths is not a round number in modern usage, but it was a standard, named unit in Roman law. Confusing dextans (ten-twelfths) with deunx (eleven-twelfths) or bes (eight-twelfths, two-thirds) is an easy error. The full duodecimal ladder should be consulted as a set.
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Historical Dictionary Support
Black's (1st Ed.), Black's (2nd Ed.), and Burrill's are in complete agreement: dextans equals ten unciae, or ten-twelfths of the as, equivalent to five-sixths. All three cite 2 Bl. Comm. 462, note m as their primary authority; Burrill adds a secondary citation to Taylor's Civil Law, 492. The entries are nearly identical across all three sources, which reflects the narrow, technical, and uncontested nature of the term — there was simply nothing to dispute.
What the historical dictionaries do not provide is any practical illustration of how dextans operated in Roman succession or property transactions, nor do they situate the term within the broader duodecimal system of the as. A researcher encountering the term in context needs to work outward from these bare definitions to understand the full fractional vocabulary. The Latin sources, including Varro and Columella, confirm that the word is a contraction of de and sextans — the as with one sextans (one-sixth, or two unciae) removed — and that the term was largely post-Augustan in usage, with Cicero preferring a circumlocution rather than the contracted form. This etymological and usage note from the Latin tradition adds texture that the legal dictionaries omit entirely.
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