Definition
In Roman law, centesima (also rendered usura centesima) denoted a rate of interest equal to one hundredth of the principal per month, yielding twelve percent per annum. The term derives from the Roman method of calculating interest: the principal was divided into one hundred parts, and one such part was permitted to be collected each month. This rate represented the maximum lawful rate of interest under Roman law. The month, not the year, was the Romans' base unit for reckoning interest, making the centesima a monthly figure that compounded to an annual rate of twelve percent.
Common Confusion
The term centesima is sometimes loosely glossed as simply "one hundredth part" — an accurate but incomplete translation that obscures its specific legal function. In Roman legal sources, centesima almost invariably refers to this monthly interest rate, not to any arbitrary hundredth fraction. Researchers encountering the bare phrase "one hundredth part" in a legal dictionary entry should confirm from context whether a general fractional meaning or the interest-rate meaning is intended.
Why It Matters in Research
Centesima is a term of Roman law with no direct survival in Anglo-American common law doctrine, but it appears in English legal literature primarily through Blackstone's Commentaries and the annotated sources that followed. Researchers working in the Law Mind corpus will encounter it most often in historical commentary on usury law, where writers traced the English regulation of interest back to Roman antecedents. The key navigational point: when centesima appears in an English legal source, it is almost always a reference point for comparative or historical argument about usury ceilings, not a term of operative domestic law.
The Blackstone citation (2 Bl. Comm. 462, note) is the anchor for virtually every English-language dictionary treatment of this term. Rapalje & Lawrence, Burrill, and both editions of Black's all trace back to it. Researchers should be aware that the historical dictionaries are largely repeating Blackstone's note rather than drawing on independent Roman law sources. For deeper engagement with the Roman law context, the dictionary entries are a starting point only.
The distinction between monthly and annual reckoning matters for any research touching on comparative usury history. English and later American usury statutes expressed rates annually; Roman law expressed them monthly. A researcher comparing ancient and modern interest limits must account for this structural difference to avoid misreading the centesima rate as equivalent to a modern one-percent-per-annum figure.
Historical Dictionary Support
The four source dictionaries are in close agreement. All define centesima as one percent per month or twelve percent per annum under Roman law, and all identify it as the highest permitted rate. Burrill provides the most substantive explanation, describing the Roman computational method — dividing the principal into one hundred parts and permitting one part monthly — in a way that clarifies why the term means what it does rather than simply stating the figure. Rapalje & Lawrence and both Black's editions are more compressed, with the second edition of Black's adding the explicit note that the month was "the unit of time from which the Romans reckoned interest," a useful precision absent from the first edition.
None of the historical dictionaries venture beyond Blackstone's commentary or engage Roman primary sources directly. Researchers needing the original Roman law context — including whether and how the centesima rate was enforced, modified, or evaded in classical and post-classical Roman practice — will need to move beyond the English legal dictionary tradition entirely.
Jurisdictional Note
Centesima is a term of Roman law with no operative jurisdiction in modern common-law systems. Its appearance in American or English legal sources is invariably historical or comparative. No U.S. jurisdiction has adopted the term as part of domestic usury doctrine.