Definition
A Latin term meaning an interval of time or, less commonly, of place. In legal usage, *intervallum* appears almost exclusively in the context of mental incapacity, where it denotes a temporary period of restored reason or sanity occurring within a broader state of mental disorder. The phrase *lucida intervalla* (lucid intervals) — built on this root — is the operative concept: a window during which a person otherwise regarded as lacking legal capacity could nonetheless act with legal effect, as in executing a will or entering a contract.
The term is rarely encountered as a standalone substantive. It functions primarily as a component within Latin maxims and formulations carried forward from medieval English law.
Common Language
Modern common usage (Wiktionary): An interval; also, the gap between an outer rampart and the fortress it surrounds.
Historical common usage (Webster's 1913): An interval. Illustrated with Shakespeare's use: "And a' shall laugh without intervallums."
The common meaning is essentially geometric or temporal — a space or gap between two things. The legal meaning narrows this sharply: *intervallum* in legal sources almost always refers to a gap in mental incapacity, not a gap in time or physical space generally. A researcher encountering the word in a common literary or architectural context will find it unhelpful; in a legal text, the word signals a question about mental competency and legal capacity.
Common Confusion
*Intervallum* and *lucida intervalla* are not the same thing, though they are closely related. *Intervallum* is the noun denoting the interval itself; *lucida intervalla* is the established legal phrase meaning "lucid intervals" — the plural, qualified form that carried actual doctrinal weight in English and civil law. Burrill cites Bracton using both the singular (*lucidis intervallis*) and the qualified form (*dilucidis intervallis*) in different passages. A researcher should treat *intervallum* as the building block and *lucida intervalla* as the operative doctrine.
Why It Matters in Research
*Intervallum* will not appear often as a headword in legal sources, but it appears frequently embedded in Latin passages from medieval English legal texts — Bracton and Fleta in particular — that deal with the legal standing of persons with mental disorders. Any research touching on testamentary capacity, contractual capacity, or the legal status of the mentally ill in historical English law will encounter this term within those Latin formulations.
The key navigational point: when you see *intervallum* in a source, you are likely looking at a capacity question, not a procedural or temporal one. The doctrinal substance lives under *lucida intervalla*, and that is where the research chain should continue.
Burrill's citations to Bracton fol. 12, fol. 43, and fol. 420b, and to Fleta lib. 6, c. 40, §1 and lib. 2, c. 60, §2, are the primary textual anchors for this term in the English common law tradition. Both Bracton and Fleta are available in scholarly editions and are part of the Law Mind corpus. The passages are worth locating in full because they give the earliest English-language legal framework for when a person's acts during a lucid interval would be treated as legally valid.
The phrase *ex intervallo* (after an interval) also appears in Fleta in a procedural context, meaning that some legal act was performed or effect arose following a gap in time. This usage is distinct from the capacity context and should not be conflated with the lucid-interval doctrine.
Historical Dictionary Support
Burrill is the sole historical dictionary source for this term, and his entry is lean but precise. He identifies *intervallum* as Old English law Latin, provides two direct quotations from Bracton using the term in the context of lucid intervals, and notes the *ex intervallo* usage from Fleta. He does not define the doctrinal content of lucid intervals here — that is handled under *lucida intervalla* — treating *intervallum* correctly as a component term rather than a substantive doctrine.
Webster's 1913 confirms the common literary usage, citing Shakespeare, and acknowledges the word is rare in ordinary English. Neither Webster's nor Wiktionary addresses the legal dimension. There is no divergence among sources on basic meaning; the value of the legal dictionary entry is the doctrinal context that general dictionaries do not supply.
Jurisdictional Note
The lucid-interval doctrine derived from Bracton and Fleta was carried into English common law and from there into American law. The underlying Latin terminology (*intervallum*, *lucida intervalla*) is most relevant to pre-modern sources; modern capacity doctrine uses the same concepts under contemporary English-language formulations. Civil law jurisdictions developed parallel capacity frameworks using similar Latin roots.