Definition
A Latin term from Roman and common law meaning designation or specification — the act of pointing out, naming, or identifying a particular person or thing with legal precision. It appears most often in two contexts:
1. Designatio personae: The designation or identification of a specific person in a legal instrument, particularly in contracts, conveyances, and devises. The term distinguishes the act of identifying who takes under a document from the terms describing what they take or how long they take it.
2. Designatio as a canon of construction: In the interpretation of legal instruments, designatio carries the implication that naming one person or thing operates to exclude others not named — captured in the maxim designatio unius personae est exclusio alterius (the specification of one person is the exclusion of another).
Common Confusion
Designatio personae is sometimes read as interchangeable with a word of limitation — a term that defines the extent or duration of an interest. The distinction is substantive: designatio personae identifies who receives the interest (a word of purchase); a word of limitation defines the estate they take. In older property instruments this distinction determines whether language creates a life estate, a fee simple, or something else. Conflating the two can produce serious misreading of historical deeds and wills.
Why It Matters in Research
Researchers working in early English and American property law, wills, and conveyancing will encounter designatio in two distinct research problems.
First, instruments from the seventeenth through nineteenth centuries use designatio personae to resolve ambiguity about whether a named party is taking in their own right (purchase) or whether the naming language is defining the scope of a prior taker's estate (limitation). The line between these functions is not always clear on the face of old instruments, and courts litigated it extensively. Understanding designatio personae as a word of purchase is essential to correctly reading those cases and the treatises interpreting them — particularly Powell on Devises and Hilliard on Real Property, both cited in Burrill.
Second, the exclusionary maxim (designatio unius est exclusio alterius) is a variant of the broader expressio unius canon. Researchers should be careful: in historical sources the designatio framing emphasizes persons, while expressio unius is more often applied to things, classes, or powers. The two canons share the same logical structure but carry different case law lineages and appear in different doctrinal contexts. Treating them as identical can cause researchers to miss controlling authority that uses one label but not the other.
Because designatio appears almost exclusively in Latin form in primary sources, keyword searches limited to English equivalents will miss most occurrences. Searching "designation of the person," "word of purchase," and the full Latin phrases — including variant spellings like designatio personæ — is necessary for comprehensive retrieval.
Historical Dictionary Support
Burrill provides the more complete treatment. He defines designatio with reference to Powell on Devises and Hilliard's Real Property, situating it firmly in the law of wills and real property conveyancing. He distinguishes designatio personae as a word of purchase against words of limitation — a distinction central to estate law. He also records the exclusionary maxim with attribution to Coke on Littleton (Co. Litt. 210), grounding the canon in a source that shaped centuries of common law property doctrine.
Anderson's entry is brief, pointing out the meaning and directing the reader to compare related terms, but adds little analytical content. For most research purposes, Burrill is the more useful historical dictionary source on this term.
Neither dictionary addresses civilian (Roman law) uses of designatio in any depth, nor do they treat its appearance in continental or Scottish legal sources. Researchers working in mixed jurisdictions or comparative law contexts should not rely on these entries alone.
Jurisdictional Note
Designatio personae as a doctrinal concept is most developed in English common law and early American jurisdictions following English property law traditions. Louisiana and other mixed-jurisdiction states with civilian heritage may encounter designatio in a different Roman law context, where its meaning and application can diverge from the common law treatment in Burrill and Anderson.