Definition
Res fungibiles (Latin: "fungible things") is a term from Roman and civil law referring to things that are interchangeable by nature — goods or commodities where any one unit is the equivalent of any other unit of the same kind, quality, and quantity. When a thing is res fungibiles, its value lies in its type and measure, not in its individual identity. Money is the paradigmatic example: one dollar is interchangeable with any other dollar. Grain, oil, wine, and generic bulk commodities were the classical illustrations.
The practical consequence in law is significant. When fungible things are transferred, the recipient typically acquires ownership of the specific units received and incurs an obligation to return not those same items, but an equivalent quantity and quality. This is the foundation of the mutuum — the Roman loan of consumption — where the borrower consumes the thing and owes back its equivalent, not the identical object.
Common Confusion
Res fungibiles is the Latin civil-law term. Its common-law counterpart concept is simply "fungible goods" or "fungibles," used without the Latin form in modern Anglo-American commercial law. The concepts are substantively identical, but researchers must recognize that historical civil-law sources and early American treatises drawing on Roman law will use the Latin form, while modern UCC-era sources will not. Confusing res fungibiles with res (things generally) or treating it as a subtype of res incorporales (intangible things) is an error: fungibility is about interchangeability, not tangibility.
Why It Matters in Research
Res fungibiles is primarily a term of art in civil-law systems and in American legal scholarship that draws directly on Roman law sources — treatises, early civilian writers, and comparative law materials. It will not appear with any frequency in common-law case reporters. Researchers working in pre-twentieth-century American legal literature, particularly in jurisdictions with civil-law heritage (Louisiana, California in its early period, Texas), may encounter it in contract and property discussions.
The concept matters substantively in several research contexts:
First, in bailment and loan research: the distinction between a bailment of non-fungible goods (where the identical thing must be returned) and a mutuum of fungible goods (where equivalent goods are returned) is foundational. Tracing this distinction requires understanding res fungibiles as its civil-law anchor.
Second, in commercial law and UCC research: modern Article 9 (secured transactions) and Article 7 (documents of title) both grapple with fungibility in warehousing and commodity financing. The conceptual lineage runs through res fungibiles even when the Latin term is absent.
Third, in trust and property research: co-mingling of fungible goods raises distinct ownership questions that early American courts sometimes addressed through civil-law categories. A researcher tracing the doctrinal history of commingling — particularly in grain elevator cases or banking deposit cases — will find res fungibiles lurking behind the analysis even when unnamed.
The term presents a navigational trap: Rapalje & Lawrence's entry cross-references res gestae materials in a way that appears mid-entry, reflecting the compressed cross-reference style of nineteenth-century legal dictionaries. Researchers should not infer any connection between res fungibiles and res gestae — they are entirely unrelated doctrines sharing only the Latin noun res.
Historical Dictionary Support
Black's and Burrill's are in complete agreement: both define res fungibiles tersely as "fungible things" and redirect to that substantive entry, treating the Latin form as a pointer rather than a term requiring independent elaboration. This economy reflects the reality that the concept's weight was carried by the vernacular term "fungibles" and by the detailed civilian treatise literature rather than by dictionary entries.
Rapalje & Lawrence's entry is notable for what it reveals about nineteenth-century dictionary method: the res fungibiles entry cross-references to "FUNGIBILES RES" (the inverted form), but the printed entry then bleeds into res gestae materials — almost certainly a typographic artifact of the original publication. This underscores a practical warning for corpus researchers: nineteenth-century dictionary pagination errors can create false associations between entirely unrelated legal concepts.
None of the three historical sources provide substantive independent treatment. For the actual doctrine, researchers must go beyond dictionary entries to civilian treatises — Pothier's work on obligations, and American writers such as Story on Bailments, who translated civil-law fungibility concepts into common-law discourse.
Jurisdictional Note
The Latin term is essentially confined to civil-law jurisdictions and to scholarly or comparative legal writing. Louisiana sources are the most likely American venue for the term appearing in its Latin form. In all other American jurisdictions, the concept operates under the English label "fungible goods" or "fungibles" without the Roman terminology.