Definition
Acra (plural: acrae) is the Latin form of "acre" as it appears in medieval English legal documents and records. In old English law, acra denotes a unit of land measurement, equivalent to the acre, used in charters, pleadings, and conveyances to describe parcels of arable land, meadow, woodland, and similar ground. The term appears almost exclusively in Latin-language legal instruments predating the general adoption of English in formal legal writing.
The term is not a term of art in the sense of carrying specialized legal content beyond its function as a unit of measurement; its significance for researchers lies in recognizing it as the Latinized form of "acre" when encountered in primary sources.
Common Language
Modern common usage (Wiktionary): In modern anatomical and medical usage, "acra" refers to the vascular areas of the body most removed from the heart — the extremities such as the hands, feet, and head.
Historical common usage: The classical Latin acra (from Greek akra) denotes a promontory or headland — a point of land projecting into water.
Neither the anatomical nor the geographical meaning has any connection to the legal use. Researchers encountering acra in a medieval English charter or legal record should not allow either the modern medical sense or the classical geographical sense to mislead them. Context — land conveyances, surveys, pleadings — will almost always confirm the land-measurement reading.
Common Confusion
Three distinct Latin or Latinate words converge on the spelling acra or similar forms: (1) the land measure (acra = acre), (2) the classical geographical term for a promontory (acra, from Greek akra), and (3) the modern medical usage. In English legal sources, only the first applies. The risk of confusion is highest when a researcher encounters acra in a document that also contains geographical description — a charter might describe land bounded by a headland — but context and the surrounding units of measurement (carucates, roods, virgates) will typically resolve any ambiguity.
Why It Matters in Research
Researchers working in the Law Mind corpus will encounter acra almost exclusively in two contexts: (1) transcriptions or facsimiles of Anglo-Saxon and early Norman charters, and (2) Year Book pleadings and Fleta-era treatise passages that retain Latin terminology. Burrill cites Fleta lib. 2, c. 71 and Coke on Littleton 5b as reference points, placing acra firmly within the classical common law treatise tradition.
The practical trap is OCR and transcription error. In manuscript sources, acra and its plural acrae are frequently misread as other words — particularly where minuscule handwriting conflates letters. A corpus search for "acre" in Latin-text documents will miss instances spelled acra or acrae; researchers must search both forms.
Acra also signals document age and register. Its presence in a source is a strong indicator that the document predates the Pleading in English Act 1362 or is a legal treatise drawing on pre-1362 forms. This helps researchers calibrate which interpretive tools apply.
The unit itself — the acre — had variable content in medieval England. An acra in a Domesday-era charter is not necessarily the same quantity of land as a modern statute acre. Researchers using acra to reconstruct landholding size should consult the relevant entry on acre and carucate, since the two units interact throughout medieval land records.
Historical Dictionary Support
Burrill's Law Dictionary provides the foundational entry, identifying acra as "[pl. acrae.] L. Lat. In old English law. An acre." Burrill supports this with references to Spelman, Fleta, Coke on Littleton, and Townshend's Pleadings, and illustrates with a passage from a charter of King Eadred (mid-10th century) — "duas carucatas terrae, et dimidiam, et 26 acras prati, et 50 acras silvae, et 70 acras de brushe" — translated as two and a half carucates of arable, twenty-six acres of meadow, fifty acres of wood, and seventy acres of brush.
No other historical legal dictionary in the current Law Mind shelf addresses acra independently. Spelman's Glossary (referenced by Burrill) is the principal authority for the term in the antiquarian legal tradition. The historical sources collectively treat acra as settled and uncontroversial — it is a Latin form, nothing more — and none suggests any disputed meaning within legal usage.
Jurisdictional Note
Acra as a legal term is specific to English legal records and instruments. It does not appear as a term of art in Scots, Irish, or continental legal traditions in the same way, though Latin acre-equivalents appear in comparable European medieval documents under different forms.