Definition
In old English law, a unit of linear measure. The term appears in legal and administrative texts as a measure of cloth or distance, but its precise modern equivalent was contested. Burrill records that the word is generally translated as "ell" in the books, but notes that Dyer expressly states ulna means a yard, not an ell. Blackstone reconciles the two positions by observing that the ancient ell answers to the modern yard, suggesting the apparent conflict reflects terminological drift rather than a genuine difference in the underlying measure. As a practical matter, the ulna in English legal contexts is best understood as a yard-length unit, though researchers must treat the term cautiously when encountered in early medieval sources where measurement standards were less fixed.
Common Language
Modern common usage (Wiktionary): The bone of the forearm extending from the elbow to the wrist on the side opposite to the thumb.
Historical common usage (Webster's 1913): The postaxial bone of the forearm; also, an ell or a yard (citing Burrill).
The anatomical meaning is the dominant modern sense and will be the first meaning a researcher encounters in any general reference. The legal meaning — a unit of linear measure — is entirely obsolete in practice. Webster's 1913 preserved both senses, reflecting a period when the legal-historical usage was still known to educated readers. Today, a researcher encountering ulna in a legal document must consciously set aside the anatomical meaning and read the term as a measurement unit.
Common Confusion
Two confusions attend this term in historical legal research. First, the ell/yard question: translators and copyists have rendered ulna inconsistently, sometimes producing "ell" and sometimes "yard" in the same body of sources, creating apparent discrepancies in measurements that are not discrepancies in the underlying standard. Second, the term should not be confused with pertica (rod or perch), virgata (virgate, a land measure), or other Latin linear terms that appear nearby in medieval administrative records. Ulna in its legal sense is specifically a cloth-and-short-distance measure, not a land measure.
Why It Matters in Research
Researchers working with medieval English statutes, manorial records, or market regulation documents will encounter ulna in contexts governing the sale of cloth, the width of roads or lists, and the standardization of commercial measures. The Magna Carta citation in Burrill (c. 25, duae ulnae infra listas — two ells within the lists) places the term directly in a constitutional document, meaning it can surface in commentary and case law that glosses Magna Carta provisions on weights and measures.
The ell/yard ambiguity is a genuine research trap. When a source translates ulna as "ell," the researcher cannot assume this reflects a different underlying measure from a source that says "yard." Blackstone's harmonizing note in 1 Bl. Com. 275 is the most useful anchor: treat the ancient ulna as equivalent to the modern yard for English legal purposes unless context strongly suggests otherwise.
The Scotch variant is a separate issue. Burrill notes that the Scots eln or elne tracked the Latin ulna more closely than the English word did, meaning that in Scottish legal sources the term may carry slightly different proportions. Cross-border commercial disputes or records involving both English and Scottish parties may require attention to which standard applies.
The term has no living legal significance. Its research value is purely historical and textual.
Historical Dictionary Support
Burrill is the only historical legal dictionary in the present corpus to treat ulna, and the entry is compact but precise. Its key contribution is surfacing the Dyer reference — a primary source directly stating that ulna equals yard, not ell — and pairing it with Blackstone's reconciling observation. The entry does not resolve whether the ell and the ancient yard were ever meaningfully different in practice, nor does it address the variability of the ell across different English regions and periods. Researchers needing fuller treatment of historical measurement standards should consult specialized works on medieval English metrology, as legal dictionaries of the period treat the term as a settled curiosity rather than a live interpretive problem.
Jurisdictional Note
The yard/ell ambiguity has a Scottish dimension: the Scots eln diverged from the English yard in later usage, so the same Latin term may point to different physical lengths depending on the jurisdiction of the source document. English legal contexts default to the yard reading per Blackstone; Scottish contexts warrant independent verification against Scottish measurement authorities.