Definition
Latin phrase meaning "in delay" or "in default." A party is said to be in mora when they have failed to perform an obligation at the time it was due — particularly when a borrower omits or refuses to return a loaned thing at the appointed time. The concept originates in Roman and civil law and carries specific legal consequences, including the shifting of risk of loss to the defaulting party and potential liability for damages arising during the period of delay.
The phrase functions as a status designation: once a party is adjudged in mora, they bear responsibility for any deterioration or loss of the subject matter that occurs after the point of default, even where such loss would otherwise have fallen on the opposing party.
Common Language
Modern common usage (Wiktionary): "In default."
The Wiktionary gloss is technically accurate but strips the phrase of its operative legal content. In ordinary usage, "default" broadly suggests failure or absence. In legal usage, in mora carries a specific civil-law meaning tied to the timing of performance obligations, risk allocation, and the debtor-creditor relationship — consequences that the plain phrase "in default" does not convey on its own.
Recognized Forms
/SUBTYPES
The civil law tradition distinguishes between mora debitoris (delay on the part of the debtor) and mora creditoris (delay on the part of the creditor — i.e., unreasonable refusal to accept performance). The historical dictionary sources address only the debtor-side usage, but researchers working in civil-law contexts should be alert to both forms.
Why It Matters in Research
In mora is a civil-law term and will appear most frequently in sources drawing on Roman law, Louisiana law, Scots law, and continental jurisprudence. Researchers working in common-law jurisdictions should treat it as a borrowing that appears in treatises on bailment and contract more than in case law. Its operational significance in a given source depends heavily on the legal system being applied.
Burrill adds a Scots law dimension absent from the other dictionaries: in Scottish practice, a creditor who has commenced but not completed the diligence necessary to attach a debtor's property is said to be in mora. This is a distinct usage — creditor-side, procedural rather than substantive — and researchers consulting Scots or early American sources influenced by Scots legal practice should not assume the phrase refers only to debtor default.
The Story on Bailments citations (§§ 254, 259) appearing across all four dictionaries point to a single authoritative treatise source. This clustering suggests that 19th-century American legal dictionaries drew on Story rather than on independent case law to define the term. Any researcher tracing the concept into early American jurisprudence should go directly to Story rather than treating the dictionary definitions as independent authorities.
The phrase also appears in the maxim in majore summa continetur minor ("in the greater sum is contained the less"), which appears adjacent to in mora in the second edition of Black's. Researchers scanning historical dictionary pages should take care not to conflate these separate entries.
Historical Dictionary Support
All four source dictionaries agree on the core definition: in mora means "in delay" or "in default," and the canonical illustration involves a borrower who fails to return a loaned thing at the proper time. Burrill provides the fullest entry, adding both the Latin-to-French equivalence (en demeure) and the Scots law usage drawn from Bell's Dictionary. Rapalje & Lawrence and Black's (2nd ed.) track Story on Bailments directly, using nearly identical language. Black's first edition is fragmentary in the available text but consistent with the others.
No source dictionary provides extended treatment of mora creditoris or of the Roman law doctrine underlying the term. Researchers needing depth on the civil-law framework will find the dictionary entries insufficient and should consult treatises on civil obligations or Roman private law directly.
Jurisdictional Note
The term retains operational force in Louisiana, where civil-law principles govern private obligations, and in jurisdictions with significant civil-law influence. In Scots law it carries the specialized procedural meaning noted above. In most common-law jurisdictions, the concept is addressed through doctrines of breach, anticipatory repudiation, and conditions precedent without invoking the Latin phrase.