Definition
In Roman civil law, the mother of a wife's mother — that is, a wife's maternal grandmother. The term is Latin, drawn from the vocabulary of Roman family law, and appears in the Digest of Justinian as part of the systematic classification of cognate and affine relationships. By extension, the term could also encompass the paternal grandmother of a wife, depending on context, though its primary recorded usage designates the grandmother on the wife's side within the hierarchy of familial degrees.
Why It Matters in Research
PROSOCRUS is a term of pure Roman law taxonomy, encountered almost exclusively in sources tracing the civil law tradition: the Corpus Juris Civilis, its medieval glossators, and early modern commentators working in the civilian tradition. Researchers are unlikely to encounter it in common law materials, as English law did not adopt the Roman system of kinship nomenclature in its technical form.
The term matters most in three research contexts. First, in historical intestacy and inheritance research: Roman law calibrated succession rights by precise degrees of relationship, and terms like PROSOCRUS anchor a specific position in that scheme. Confusing or overlooking these granular designations can cause a researcher to misread who qualified as an heir or claimant under a given text. Second, in research touching Roman marriage law and the law of affinity: the -socrus root signals a relationship by marriage (affinity) rather than blood (cognation), a distinction Roman law treated with considerable precision. Third, in comparative law and canon law research: medieval canonists, working to define prohibited degrees of marriage, borrowed and adapted Roman kinship vocabulary, and PROSOCRUS (or its equivalents) could appear in ecclesiastical sources governing consanguinity and affinity tables.
Burrill's citation to Digest 38.10.4.6 is the entry point for any deeper research. That section of the Digest addresses the classification of cognates and their degrees, and reading PROSOCRUS in context there clarifies both its precise meaning and its place within the Roman system of reckoning relationship for legal purposes.
Historical Dictionary Support
Burrill's Law Dictionary provides the only dictionary entry among Law Mind's shelf sources. His definition is economical: "a wife's grandmother," with a citation to the Digest. This is accurate as far as it goes but omits the affinal character of the relationship — PROSOCRUS is not the husband's own grandmother but his grandmother-in-law, a distinction that matters when degrees of affinity are being calculated. Burrill appends the Greek term ΠΡΟΣΩΠΟΝ (person) immediately following this entry, which reflects the original dictionary's arrangement by headword proximity rather than any substantive connection between the two terms.
No common law dictionary in the standard corpus — not Black's, not Bouvier, not Tomlins — carries this term, which reflects its essentially civilian provenance. Researchers relying solely on common law reference works will find no guidance here and should go directly to civil law sources and their commentators.
Jurisdictional Note
This term has no operative meaning in modern common law jurisdictions. It is relevant only in historical research into Roman law, its medieval civilian successors, and canon law systems that adopted Roman kinship nomenclature.