Definition
Acceleration, in law, refers to two related but distinct concepts sharing a common core idea: the speeding up of a legal right or obligation that would otherwise arise at a later time.
1. Acceleration of an expectant interest (property law): The shortening of the time for the vesting in possession of an expectant or future interest. When an intermediate estate or prior interest fails, is disclaimed, or is otherwise cut short, the interest that would have followed it may "accelerate" — that is, vest sooner than originally contemplated. A remainder that was not expected to become possessory until some future event may fall into possession immediately upon the premature termination of the preceding estate.
2. Acceleration of a debt or obligation (contract and lending law): The act of making an entire debt or obligation due and payable immediately, triggered by the borrower's default or by the occurrence of a specified condition. This is the more frequently encountered meaning in modern legal practice. Lenders exercise the right of acceleration — typically granted by an acceleration clause in a note or mortgage — to declare the full unpaid balance due upon default, rather than waiting for each installment to mature in turn.
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Common Language
Modern common usage (Wiktionary): The act of accelerating or the state of being accelerated; increase of motion or action; increase of speed or velocity, as opposed to deceleration or retardation.
Historical common usage (Webster's 1913): The act of accelerating or the state of being accelerated; increase of motion or action, as a falling body moves toward the earth with an acceleration of velocity — opposed to retardation.
The ordinary meaning captures pure physics: things moving faster. The legal meanings invert the intuitive frame in a significant way. In property law, acceleration describes rights arriving sooner than expected — a temporal compression of future interests. In debt law, it describes an obligation becoming due all at once rather than gradually. Neither usage maps cleanly onto the layperson's sense of something simply "speeding up."
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Recognized Forms
/SUBTYPES
Acceleration clause (also: acceleration provision): A contractual clause, standard in mortgages and promissory notes, authorizing the creditor to declare the entire unpaid balance immediately due and payable upon a specified default or triggering event. The clause is the mechanism; acceleration is the act of invoking it.
Acceleration of a remainder or future interest: Occurs in property law when a prior estate terminates early — by disclaimer, forfeiture, merger, or failure of condition — causing the remainder or executory interest to vest in possession ahead of schedule.
Optional vs. automatic acceleration: Some acceleration clauses are automatic (the full debt becomes due by operation of contract upon default without any affirmative act); others are optional, requiring the lender to elect acceleration. The distinction affects cure rights and foreclosure procedure in most jurisdictions.
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Why It Matters in Research
The two meanings inhabit almost entirely separate bodies of law and literature. A researcher working on mortgage foreclosure is dealing with acceleration in its contractual debt sense; a researcher working on future interests in property is dealing with acceleration in its vesting sense. Conflating them produces wrong turns.
In the foreclosure context, acceleration is a procedural prerequisite in most jurisdictions — the debt must be properly accelerated before foreclosure can proceed. Researchers examining historical foreclosure records, deed of trust instruments, or mortgage litigation should look for the acceleration notice as a distinct step. Whether acceleration was validly made (proper notice, proper election, proper triggering event) is a recurring litigation issue. Some jurisdictions also recognize a borrower's right to cure after acceleration, which restores the original payment schedule and de-accelerates the debt; the interplay between acceleration, cure, and reinstatement varies considerably across state statutes and loan documents.
In the future interests context, acceleration problems arise most acutely in the law of wills and trusts: when a life tenant disclaims or a prior interest fails for some reason, whether the remainder accelerates depends on the instrument's language and applicable rules of construction. This distinction matters when reading older treatises and cases, which often discuss acceleration of remainders as a stand-alone doctrine without any connection to the debt-acceleration concept.
Historical sources use the term almost exclusively in its property/vesting sense. Researchers using Bouvier's or early editions of Black's should be aware that the debt acceleration meaning — now dominant in commercial practice — receives little or no treatment there. Do not assume an absence of doctrine; the lending-law usage simply developed later and in a different doctrinal stream.
The encyclopedia entry on Cost Segregation (realestate_84) addresses accelerated depreciation under tax law — a related but distinct concept (the IRS allows certain assets to be depreciated faster, "accelerating" the tax deduction). That usage is regulatory and tax-driven, not contractual or property-vesting in character, and should not be conflated with either primary legal meaning.
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Historical Dictionary Support
All three historical sources — Black's (1st Ed.), Black's (2nd Ed.), and Bouvier's — define acceleration identically and briefly: "the shortening of the time for the vesting in possession of an expectant interest," with Bouvier's attributing the formulation to Wharton. The uniformity is notable; all three sources were capturing the same narrow property-law doctrine and nothing more.
None of the historical dictionaries address acceleration in the debt or contract sense. This is a genuine gap. The contractual acceleration clause became a standard feature of American mortgage and commercial lending practice during the late nineteenth and early twentieth centuries — precisely the period these dictionaries were being compiled — but the lending usage does not appear to have been considered dictionary-worthy at the time, or was treated as self-evident from the clause's language. A researcher finding "acceleration" in a nineteenth-century treatise index should expect the property/vesting meaning; a researcher encountering the term in early twentieth-century commercial loan instruments is almost certainly looking at the debt meaning, even without dictionary support from that era.
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Jurisdictional Note
Acceleration of mortgage debt is heavily regulated by state law. Some states require notice and an opportunity to cure before a valid acceleration; others permit acceleration on demand following default. Whether a borrower can reinstate a loan and de-accelerate after the lender has exercised the option varies by statute and contract. Researchers should not assume uniform procedural rules across jurisdictions.
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Encyclopedia Cross-Reference
Foreclosure — Overview, Default, Acceleration, and the Right to Cure (The Law Mind Real Estate Transactions & Construction Encyclopedia)
Promissory Notes — Terms, Acceleration Clauses, Due-on-Sale, and Negotiability (The Law Mind Real Estate Transactions & Construction Encyclopedia)
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