Definition
Amortisement is an archaic legal term for the alienation of lands or tenements into mortmain — that is, the transfer of real property to an ecclesiastical body, religious house, or other corporation incapable of alienating it further. The effect of such a transfer was to place the land permanently beyond the reach of feudal services and inheritance, extinguishing the lord's expectation of relief, wardship, and escheat. The term is functionally synonymous with amortization in its older property law sense and is closely tied to the doctrine of mortmain.
Common Language
Modern common usage (Wiktionary): A synonym of amortization — the gradual reduction of a debt or the spreading of costs over time.
Historical common usage (Webster's 1913): Not separately defined; subsumed under amortization, which Webster's treats primarily as the extinguishment of a debt or the act of conveying property to a corporation in perpetuity.
The gap between common and legal meaning is significant and reflects a complete historical reversal of emphasis. In modern usage, amortization is almost exclusively a financial term — the scheduled paydown of a mortgage or loan. In its older legal sense, amortisement had nothing to do with debt reduction; it described the permanent alienation of land into a form of perpetual, inalienable corporate ownership. A researcher encountering amortisement in a historical legal text should not import any financial meaning.
Common Confusion
Amortisement, amortization, and mortmain are distinct but interlocking concepts that historical sources treat inconsistently. Amortisement is the act of alienating land into mortmain. Mortmain is the condition or status of land so held — literally "dead hand," describing corporate ownership that never dies and therefore never triggers feudal incidents. Amortization, in the historical property sense, is effectively the same act as amortisement, but the spelling and phrasing vary across sources and centuries. Modern readers who know amortization only as a financial term will misread every historical occurrence of both words in a property law context.
Why It Matters in Research
Amortisement is a term you will encounter almost exclusively in historical English property law sources — Year Books, early treatises, and dictionaries organized around feudal tenure. It does not appear in American legal materials with any frequency, and where it does appear it is either a deliberate archaism or a direct quotation from an English source.
The primary research trap is the financial meaning carried by the modern cognate. Any corpus search for amortization or amortisement across a mixed historical and modern collection will surface both property-law and financial-law materials, and the two bodies of doctrine are entirely unrelated. Filter by date and subject matter before drawing conclusions.
A secondary trap: Burrill and similar nineteenth-century dictionaries cross-reference amortisement to mortmain and move on quickly, treating the term as derivative. That brevity is accurate — amortisement has no independent doctrinal life separate from the mortmain framework. Researchers who need substantive analysis should go directly to mortmain sources rather than spending time on the act of transfer itself.
Statutes of Mortmain, beginning with the Statute De Viris Religiosis (1279) and extended by subsequent English legislation, were the primary legal response to amortisement. Those statutes are the controlling documents; amortisement is simply the transaction those statutes regulated. If your research touches this term, you are almost certainly researching the history of mortmain restrictions, ecclesiastical property holding, or the gradual dissolution of feudal tenure incidents — not a self-contained doctrine called amortisement.
Historical Dictionary Support
Burrill's Law Dictionary defines amortisement as "the alienation of lands or tenements in mortmain," notes the variant spelling amortization, and directs the reader to the mortmain entry. This is the full extent of treatment across the historical dictionary shelf — the term receives no independent elaboration in the dictionaries that include it, because it functions as a label for an act rather than as an organizing legal concept. Historical sources are in agreement on the definition; they differ only in spelling (amortisement vs. amortizement vs. amortization) and in how much of the mortmain doctrine they choose to summarize under this heading versus reserving for the mortmain entry proper.
What historical dictionaries do not address is the eventual obsolescence of the term. As mortmain restrictions were progressively abolished or transformed by statute — in England through the Mortmain and Charitable Uses Act 1888 and subsequent reforms, and in American jurisdictions that never fully adopted mortmain doctrine — amortisement lost its operative legal context and ceased to appear in new legal writing.
Jurisdictional Note
Amortisement is a term of English feudal property law and has no significant independent history in American jurisdictions. American states varied widely in whether and how they adopted mortmain restrictions, and most modern American property law has no use for the term. Researchers working in colonial American materials may encounter it in contexts derived from English practice.