Definition
Latin phrase meaning "by the year" or "for each year." Used in legal instruments, contracts, financial documents, and judgments to express a rate, obligation, or entitlement calculated on an annual basis. Most commonly encountered in clauses specifying interest rates ("interest at 6% per annum"), salary or compensation terms ("a salary of $50,000 per annum"), rent obligations, and periodic payments of any kind. The phrase signals that the stated figure is to be measured, accrued, or applied over a full twelve-month period.
Common Language
Modern common usage (Wiktionary): "In a year" or "for a year."
Historical common usage (Webster's 1913): Not separately defined; treated as a straightforward borrowing from Latin meaning "yearly" or "for each year."
The common and legal meanings are essentially the same. The legal significance lies not in any divergence of meaning but in the phrase's precision as a term of drafting: when a contract or judgment specifies a rate "per annum," courts treat that as a deliberate annual measurement that affects how accrual, proration, and default calculations are performed.
Why It Matters in Research
Per annum is a drafting term, not a substantive legal concept, so its importance in the Law Mind corpus is almost entirely contextual. Researchers encounter it most often in three settings: interest rate provisions, compensation clauses, and statutory or regulatory rate schedules.
In older instruments and decisions, the phrase sometimes appears without specifying how compounding or proration applies when a payment period is shorter than a year. Courts have had to interpret whether a stated per annum rate implies simple or compound interest, and whether partial-year periods are prorated proportionally. Researchers reading nineteenth- and early twentieth-century contract disputes should watch for this ambiguity—it is common in the case law.
The phrase also appears in statutes fixing judgment interest or statutory penalty rates. When a legislature or court rule sets interest "at X% per annum," the calculation method (daily accrual, monthly accrual, or lump-sum annual application) has been a recurring interpretive issue. Modern practice increasingly replaces per annum with explicit daily or monthly rates to eliminate ambiguity, so its frequency declines in post-1980 drafting. Researchers tracing interest calculation standards across time periods should note this shift.
Per annum is not jurisdiction-specific—it is universal across common law systems—but the statutory rates it describes vary considerably by jurisdiction and by subject matter (judgment interest, contract default interest, usury limits). The phrase itself is neutral; the rate it modifies is where jurisdictional variation matters.
Historical Dictionary Support
The historical dictionaries are unanimous and brief: per annum means "by the year," a Latin phrase retained in legal and commercial use. Black's (both editions), Rapalje & Lawrence, Bouvier's, and Burrill's all confirm this with no meaningful divergence. Burrill traces the phrase to Fleta (a thirteenth-century English legal treatise), giving it a traceable common law pedigree, though this historical root has no practical significance for modern research.
The historical sources add nothing beyond the definition itself. None of them address the interpretive questions—compounding, proration, interaction with usury statutes—that actually arise in practice. This is a case where the historical dictionaries are complete as to meaning but silent as to application, and the real research value lies in the case law rather than the dictionary shelf.
Black's 2nd Edition supports the definition with citations (Ramsdell v. Hulett, 50 Kan. 440; State v. McFetridge, 64 Wis. 130; Haney v. Caldwell, 35 Ark. 168), confirming the phrase was sufficiently litigated by the late nineteenth century to require judicial treatment—most likely in interest and compensation disputes.
Encyclopedia Cross-Reference
No Law Mind Encyclopedia entry directly addresses per annum as a drafting or calculation term. The matched entries (Negligence Per Se, Physical Takings Per Se Rules, Defamation Per Se) involve the distinct Latin modifier "per se" ("by itself" or "in itself") and are unrelated. Omitted.