Definition
A Law French term from old English law meaning "seised" or "possessed." It functions as the past participial form of seisin — the feudal concept of lawful possession of a freehold estate in land — and appears in medieval legal records and Year Books to describe a person as having been in seisin of property at a given time. The term carries the full legal weight of seisin: not mere physical occupation, but the recognized, rightful holding of a freehold estate with the standing that entailed under feudal tenure.
Common Confusion
SEISI should not be confused with the noun SEISIN (or SEIZIN), which names the legal condition or status of possession itself. SEISI is the adjectival or participial descriptor — a person is seisi of land, meaning they hold seisin of it. Researchers encountering seisi in a medieval plea roll or Year Book entry are reading a description of status, not a term for the right itself. The distinction matters when tracing chains of title or interpreting who held what at a specific moment in time.
Why It Matters in Research
This term will appear almost exclusively in Law French sources: Year Books, plea rolls, and early common law treatises predating the gradual displacement of Law French from English legal records (formalized by statute in the mid-seventeenth century, though Year Book language persisted in citation well beyond). Researchers working in pre-modern property records, feudal tenure disputes, or the history of seisin doctrine should recognize seisi as a term of art embedded in that linguistic register, not a clerical variant or corruption.
The practical trap for corpus researchers is orthographic: Law French spelling was not standardized, and seisi may appear as seisy, seisie, or in Latinized contexts as seisitus. When searching manuscript sources or early printed Year Books, variant spelling searches are essential. Burrill's citation to the Year Books (Mich. 4 Edw.) anchors the term's usage in the early fourteenth century, which helps date the linguistic register a researcher is dealing with.
Seisi also appears in formulaic conveyancing and pleading language describing the seisin of ancestors — "seisi de droit" or similar constructions — relevant to the real actions (novel disseisin, mort d'ancestor, and their kin) that dominated medieval land litigation. Understanding that seisi signals the pleading of an ancestor's or party's lawful possession at a specific time helps decode the logic of these actions, in which proof of prior seisin was a foundational element.
Researchers tracing the doctrine of seisin into Blackstone, Coke, or Littleton will find the concept fully developed in English, but the Law French form seisi in the underlying Year Book sources cited by those authors. Fleta and Bracton, both cited in the Black's 2nd edition entry, use the term in their discussions of the nature of seisin in demesne versus seisin of right — a distinction central to the forms of real action.
Historical Dictionary Support
The three source dictionaries agree entirely on the core meaning: seisi means "seised" or "possessed" in old English law. Black's (1st ed.) entry is fragmentary as extracted, but the 2nd edition entry provides useful technical context, noting the distinction between seisin "in his demesne" (applicable to corporeal hereditaments) and seisin without that phrase (applicable to incorporeal hereditaments or future estates). This distinction, drawn from Coke on Littleton and confirmed in Bracton and Fleta, is the most substantive legal content the dictionaries contribute.
Burrill adds the concrete Year Book illustration — seisi de deux juments, "seised of two beasts" — which is useful both as a linguistic example and as a reminder that seisin concepts extended in medieval law beyond land to chattels in certain contexts, though seisin's primary domain was always freehold land.
What the dictionaries do not address is the term's relationship to pleading mechanics or its role in distinguishing the various real actions — an omission that Coke, Bracton, and the Year Book reporters themselves fill more completely.