Definition
Anatocism is the practice of charging interest upon interest — that is, compounding interest so that unpaid interest is added to the principal and itself becomes subject to further interest charges. The term originates in Roman and civil law, where it described a practice regarded with suspicion and frequently subject to legal prohibition or restriction.
In modern usage, the concept survives entirely under the familiar label "compound interest," and anatocism as a standalone term is encountered almost exclusively in civil law scholarship, historical legal texts, and comparative law analysis. Where it appears in legal argument today, it typically signals a claim that compound interest has been improperly charged or that a jurisdiction's rules against anatocism — inherited from Roman or civil law tradition — bar the practice in a particular context.
Common Language
Modern common usage (Wiktionary): compound interest.
Historical common usage (Webster's 1913): "Compound interest." Marked as rare; the entry itself cites Bouvier, indicating the term was recognized as legal rather than lay vocabulary even then.
The gap here is one of register rather than meaning: common sources and legal sources agree on what anatocism describes. The significance for researchers is that the term's legal weight goes beyond mere description — in civil law systems, anatocism carried normative force as a prohibited or disfavored practice, not simply a neutral financial mechanism. "Compound interest" in modern commercial usage is standard and presumptively lawful; anatocism in historical legal texts signals a legal wrong or a category subject to regulation.
Common Confusion
Anatocism and usury overlap in the historical sources but are not identical. Black's (both editions) equates anatocism with usury, reflecting the Roman-law context in which compound interest was treated as an aggravated form of unlawful interest-taking. Bouvier is more precise, defining it functionally as taking interest on interest without the usury label. Researchers should not assume that every historical source treating anatocism as unlawful is also asserting that the applicable rate was excessive — the objection in civil law tradition was to the compounding structure itself, independent of whether the underlying rate was permissible.
Why It Matters in Research
Anatocism is a term almost entirely confined to civil law sources, comparative law scholarship, and historical legal dictionaries. Researchers working in common law materials will rarely encounter it by name; when they do, it is almost always in a treatise drawing on Roman or Continental sources, or in a Louisiana, Quebec, or mixed-jurisdiction context where civil law rules on interest survive.
Several navigational points matter:
First, the term functions as a jurisdictional signal. Its appearance in a source strongly suggests civil law influence. Common law jurisdictions addressed compound interest through usury statutes, contract law, and equity doctrine — not through a doctrine called anatocism. If a researcher encounters the term in a 19th-century American source, it is almost certainly in a civil law section, a Louisiana court, or a comparativist treatise.
Second, the prohibition on anatocism was not uniform even in civil law systems. Justinian's Code (Cod. 4, 32) addressed compound interest, but later civil codes varied considerably in whether they prohibited it outright, permitted it by agreement, or restricted it to specific contexts (e.g., merchant accounts). Researchers should not assume a blanket prohibition based on the Roman source alone.
Third, in modern commercial and banking law, compound interest is generally permissible where disclosed and agreed to. Claims invoking anatocism in contemporary litigation are unusual outside of civil law jurisdictions and are typically grounded in statutory consumer protection arguments rather than the classical doctrine.
Fourth, the term can appear in interest calculation disputes involving international contracts, where civil law parties or governing law may treat compounding differently than common law parties expect.
Historical Dictionary Support
The four source dictionaries are remarkably consistent, reflecting that this is a narrow, well-settled term of art with little doctrinal evolution within the legal dictionary tradition itself.
Black's (both editions) define anatocism as "repeated or doubled interest; compound interest; usury" and cite Cod. 4, 32, 1, 30 — a genuine reference to the Justinian Code's provisions restricting compound interest. The conflation with "usury" reflects the Roman-law framing in which compounding was categorically disfavored, not merely a question of rate.
Bouvier is slightly more careful: "taking interest on interest; receiving compound interest" — functional and descriptive, without the usury equivalence. This is the more analytically precise definition for modern research purposes.
Burrill adds nothing substantively beyond directing the reader to further discussion within his own dictionary, noting the Greco-Latin derivation.
None of the historical dictionaries address how anatocism interacts with contractual freedom, commercial exceptions, or the question — important in practice — of whether parties may agree to compound interest and thereby waive any prohibition. This is a gap researchers should be aware of when using these sources to support an argument about modern law.
Jurisdictional Note
Louisiana is the primary American jurisdiction where the civil law prohibition on anatocism has historical legal force, though Louisiana law has long permitted compound interest by express agreement. In Quebec and other mixed civil law jurisdictions, similar principles apply. Common law jurisdictions address compounding through contract and usury doctrine rather than through any equivalent of the anatocism prohibition.