Definition
A Latin term from Roman civil law meaning the coming of one person into the place of another upon that person's death — specifically, the legal succession into the estate of a deceased person at the moment of death. Successio describes the mechanism by which property, rights, and obligations passed from a decedent to those who survived and were entitled to receive them.
The term encompasses two recognized modes of succession:
1. Successio ex testamento: Succession by virtue of an express appointment made by the deceased through a valid will. The successor took the estate according to the testator's declared intent.
2. Successio ab intestato: Succession by operation of law in the absence of a valid will. The estate passed to heirs determined by the general rules of intestacy, without regard to the decedent's expressed wishes.
In Roman law, successio carried a broader conception than mere property transfer. The heir stepped into the legal personality of the deceased, assuming not only assets but also liabilities and legal relationships — a concept that left a deep imprint on civil law systems and distinguishes Roman succession from common law models.
Common Confusion
Successio is sometimes loosely equated with the English term "succession" or with the narrower concept of inheritance. The terms overlap but are not identical. Successio in Roman and civil law contexts describes the entire legal mechanism of stepping into another's legal position — universal succession — including assumption of debts and obligations, not merely receipt of assets. The common law concept of inheritance, by contrast, historically focused on descent of real property through the heir-at-law and did not carry the same universal character. Researchers working across civil and common law sources should take care not to read successio through an exclusively common law lens.
Why It Matters in Research
Successio is a term of Roman and civil law, not of the English common law tradition. Researchers encountering it in historical legal materials are almost always working with sources that draw on the Institutes of Justinian, civilian commentators, or early modern natural law and private law treatises. It does not appear as an operative term in English common law cases or statutes.
Key navigational points:
First, the term anchors a conceptual framework — universal succession — that shapes how civil law jurisdictions (Louisiana, Quebec, Scotland, and Continental European systems) structure inheritance law. When researching succession law in those jurisdictions, successio provides the foundational vocabulary that explains why heirs in civil law systems can be personally liable for a decedent's debts in ways that common law beneficiaries typically are not.
Second, in historical sources, successio will appear alongside related Latin terms including hereditas (the hereditary estate), heres (heir), legatarius (legatee), and testamentum. Understanding successio as the governing concept helps researchers map the relationships among these terms rather than treating each in isolation.
Third, the division between successio ex testamento and successio ab intestato maps directly onto the modern distinction between testate and intestate succession, but the Roman conceptual content is richer. Historical dictionaries and institutional treatises will elaborate on this distinction in ways that bare modern definitions do not capture.
Fourth, researchers using nineteenth-century American legal materials should note that civilian influence was stronger in some jurisdictions (notably Louisiana) and that writers in those traditions may use successio or its direct derivatives with technical precision that differs from usage in common law states.
Historical Dictionary Support
The three source dictionaries — Black's (1st Ed.), Black's (2nd Ed.), and Burrill — are in close agreement. All three define successio as a coming in place of another upon decease, and all three identify the two modes (ex testamento and ab intestato). The definitions draw on Justinian's Institutes (2, 9, 7) and Heineccius's Elementa Iuris Civilis, both standard authorities for Roman law in the Anglo-American legal dictionary tradition.
Burrill adds the derivation from succedere (sub + cedere, to come under or in place of), which correctly signals the term's structural meaning: not merely receiving property, but moving into the position of the predecessor. This linguistic note is more than etymological decoration — it explains the civilian concept of universal succession that gives successio its distinctive legal weight.
None of the three dictionaries develop the distinction between universal succession (successio in universum ius) and singular succession (as in a specific legacy), a distinction that would be important to a researcher working with more advanced Roman or civil law materials. For that dimension, institutional treatises such as Heineccius or Gaius's Institutes are necessary supplements.
Jurisdictional Note
Successio as a technical term of art operates within civil law jurisdictions and their legal literature. In common law jurisdictions, the concept is absorbed into the law of wills, intestacy, and estates without use of the Latin term. Louisiana's Civil Code, which preserves a civilian succession framework, provides the clearest domestic American context in which the conceptual content of successio remains operative in positive law.