Definition
An archaic Anglo-French legal term meaning an easement or privilege — that is, a right attached to land that permits its holder to make some use of another's property. The term appears in early English legal records and treatises as a variant spelling of the concept now uniformly called an easement. It carries no independent legal content distinct from the easement doctrine; it is the same concept expressed in the Law French and Law Latin vocabulary of medieval English law.
Related Latin forms include AISIAMENTUM and AYSIAMENTUM, both used in old English legal instruments and registers with the same meaning.
Common Confusion
AISEMENT should not be confused with AISNE (also spelled EIGNE), a distinct Law French term meaning "eldest" or "firstborn," used in old English inheritance contexts (e.g., aisne fitz = eldest son; aisne file = eldest daughter). The proximity of these terms in historical dictionaries and legal registers has occasionally caused transcription errors in manuscript sources. A researcher encountering either term in a medieval legal document should confirm which word is actually present before drawing conclusions about subject matter.
Why It Matters in Research
This term is almost exclusively a finding aid for historical sources. No modern practitioner uses AISEMENT; the operative term in all contemporary jurisdictions is EASEMENT. Its research value is narrow but real:
Manuscript and register research. Researchers working in early English plea rolls, Registers of Writs, or Glanvill-era materials will encounter AISEMENT and its Latin equivalents as standard vocabulary. Recognizing the term prevents misreading or skipping a passage that is in fact discussing what modern law calls an easement.
Spelling instability. Medieval Law French and Law Latin were not standardized. AISEMENT, AISIAMENTUM, AYSIAMENTUM, ESAMENTUM, and EASEMENT all appear in the corpus as variants. Corpus searches limited to a single spelling will miss the others. Any full-text search strategy for early easement doctrine must account for this orthographic range.
No independent doctrine. Unlike some archaic terms that carry legal content lost in translation to modern equivalents, AISEMENT is a straight predecessor. The substantive doctrine it describes — a right appurtenant or in gross burdening a servient tenement for the benefit of a dominant tenement — is continuous with modern easement law. The vocabulary changed; the concept did not.
Burrill cross-reference trap. Burrill groups AISEMENT, AISIAMENTUM, and AISNE in close proximity. A researcher scanning Burrill for one term may inadvertently read content belonging to the other. The definitions are short and visually similar on the page.
Historical Dictionary Support
Burrill's Law Dictionary is the sole source in the Law Mind corpus covering this term, and its entry is brief. Burrill defines AISEMENT simply as "easement; an easement" with a citation to Kelham's dictionary of Norman French, and defines the Latin form AISIAMENTUM with citations to Glanvill (lib. 12, c. 14), the Registrum Omnium Brevium (Reg. Orig. 165b), and Spelman's glossary. These citations are traceable: Glanvill's twelfth-century treatise on English law and the Register of Writs are foundational sources of English common law, and Spelman's Glossarium Archaeologicum is the standard reference for archaic legal terminology. Burrill does not provide any analysis of the substantive doctrine, treating the term purely as a vocabulary entry pointing to EASEMENT.
No other major historical legal dictionaries in the Law Mind corpus (Bouvier, Black's early editions, Tomlin) appear to carry a separate entry for AISEMENT, reflecting that even by the nineteenth century this spelling had been fully displaced by the anglicized form.
Encyclopedia Cross-Reference
See Law Mind Encyclopedia: Easements — for the substantive doctrine this term represents, including historical development, classification, and modern application.