Definition
A Latin adjective meaning "of or belonging to the night; nocturnal." In old English law, the term appears principally in the compound phrase *fur nocturnus* — a night thief — designating a thief who operated under cover of darkness. The classification carried legal significance because nighttime theft was treated as a more serious offense than daytime theft, and the category of *fur nocturnus* was explicitly distinguished from that of a burglar (*burgator*). The distinction mattered: burglary required entry into a dwelling with felonious intent; a night thief might steal without that element of breaking and entering, yet still face heightened consequences by virtue of the nocturnal circumstance.
Common Language
Modern common usage (Wiktionary): "Nocturnal; of or belonging to the night."
Historical common usage (Webster's 1913): "Of or pertaining to the night; done, occurring, or appearing at night."
The common meaning and the legal use are closely aligned — both treat *nocturnus* as simply meaning "of the night." The legal significance lies not in a departure from ordinary meaning but in the formal consequences that attached to the classification. In old English law, the word was not merely descriptive; it triggered a specific legal category with distinct treatment under the criminal law.
Common Confusion
*Fur nocturnus* and *burgator* (burglar) are easily conflated because both involve nighttime criminal activity. Burrill's source (Fleta) is explicit that they are not the same. Burglary (*burgaria*) required the breaking and entering of a dwelling house with felonious intent — a structural element absent from the night thief designation. A *fur nocturnus* stole at night but was not necessarily a burglar. Researchers encountering either term in medieval English legal sources should treat them as formally distinct categories and not assume one implies the other.
Why It Matters in Research
*Nocturnus* is not a standalone operative legal term in modern law and will not appear in contemporary statutory or case law research. Its relevance is confined to medieval and early modern English legal texts, particularly those written in Latin or drawing on the civil and natural law traditions.
Researchers working with sources such as Fleta, Bracton, or Britton — or with Grotius's *De Jure Belli ac Pacis* — will encounter *nocturnus* in its adjectival role modifying nouns of criminal classification. The critical navigational point is that the severity attached to *fur nocturnus* reflects a broader principle, traceable through both English common law and Roman law influence, that nighttime circumstances aggravate theft. This principle has a long tail: American and English statutory law long distinguished nighttime from daytime burglary and theft in grading offenses, and tracing that graduated treatment back to its roots requires understanding the *fur nocturnus* / *burgator* distinction in its original context.
Grotius's citation in Burrill (De Jure Belli, lib. 2, c. 1, § 12) is significant for researchers working on the natural law foundations of property and theft doctrine. Grotius uses the nocturnal thief as a limiting case in discussions of permissible self-defense — a night thief could lawfully be killed under certain natural law formulations where a daytime thief could not. This thread connects *nocturnus* to discussions of self-defense and necessity that persist into later legal thought.
Do not rely on modern legal databases for this term. The research path runs through Latin legal dictionaries, the text of Fleta and Bracton, and civil law treatises.
Historical Dictionary Support
Burrill's entry is concise and precise. It correctly identifies *fur nocturnus* as a night thief, correctly distinguishes it from *burgator*, and usefully cites both Fleta (lib. 1, c. 16, § 6) and Grotius. The entry does not elaborate on the legal consequences that attached to the *fur nocturnus* classification or explain why the distinction from burglary was maintained — it leaves those questions to the cited sources.
The Latin dictionary tradition (Lewis & Short) confirms the classical usage: *nocturnus* is a standard Latin adjective derived from *noctu* (by night), parallel in formation to *diurnus* (by day), and well-attested in Cicero and other classical authors. The legal use in medieval English sources is a direct application of this classical adjective to criminal classification, with no semantic shift from the ordinary Latin meaning.
No significant divergence exists among historical sources on the meaning of the word itself. The substantive legal content — what consequences followed from being a *fur nocturnus* — must be reconstructed from Fleta and related primary sources rather than from the dictionary tradition alone.
Jurisdictional Note
*Nocturnus* as a legal term of art belongs to the old English common law and its Latin-language sources, and to the broader civil and natural law tradition represented by Grotius. It has no jurisdiction-specific modern application. Researchers should treat it as a historical term whose doctrinal legacy — the aggravation of theft and related offenses committed at night — appears in varied modern forms across common law jurisdictions.